I've noticed this is a similar issue to what some other people have been experiencing, but with a seemingly different cause, so I thought I'd open a new thread rather than flood old ones. By the way, this issue occurs on all versions, as far as I could tell - I suspect it's something to do with the config files or cache, although deleting the cache did not help.

As the title implies, the land underneath the KSC disappears and is jaggedly cut off in a square. This happens when you launch a vessel and unload the initial land textures. It's hard to explain in text form, but I will include screenshots.

As you can see here, the land is there and intact most of the way up. However, as I'm sure you're familiar, the terrain makes way for a lower-res version.

This is on the descent. You can start to see the issue, there is a faint outline of the ocean cut out of the land.

Here the bug is very pronounced.

And this is just a zoom out of the area after I had crashed into the "ocean".

I'm not entirely sure how to fix the issue, but I've been troubleshooting all day with no luck. I've tried:

-The fixes here: #97

-Using an older version of Sigma Dimensions, since I am using the newest

-Deleting all mods but Sigma Dimensions and Rescale (and dependencies)

-Using multiple Rescale mods

-Fresh install of Sigma

-Deleting the cache folder

-Fresh install of KSP

-Fresh install of Kopernicus (Redundancy sake)

-Older version of Module Manager (see below)

I'll probably try a factory reset later in the week if it still isn't working.

Through process of elimination I have reduced the possibilities to this mod or Rescale, but I suspect it is this mod looking at some of the other issues, and the fact that both Rescale mods reproduce this issue.

Below is an image of my GameData folder:

That's all I can think of adding. If you need any other information I'd be happy to provide, but that's all I've got.

Update:
I rolled the game back to 1.8, with strange results. The same issue is occurring
but not to the same extent. I don't really have much of an explanation but a screenshot. (Note - This is with GPP, although I am sure this isn't the issue because this still happens on stock Kerbin)

Update:
Version in stock. Much more clear here

Update:
Found the potential issue. Your mod removes "minDetailDistance" from the latest version to fix this bug, but ModuleManager appears to write this value to the cache anyway. I'm not entirely sure though, just a guess.

Here's the section in question, found in ModuleManager.ConfigCache:

PQS
{
minLevel = 2
maxLevel = 8
minDetailDistance = 6
maxQuadLengthsPerFrame = 0.03
fadeStart = 30000
fadeEnd = 90000
deactivateAltitude = 110000
materialType = AtmosphericTriplanarZoomRotation
allowFootprints = True
Material
{
factor = 8
factorBlendWidth = 0.05
factorRotation = 135
saturation = 1.1
contrast = 1.2
tintColor = 1,1,1,0
specularColor = 0.1,0.1,0.1,1
albedoBrightness = 1.3
steepPower = 2
steepTexStart = 10000
steepTexEnd = 200000
steepTex = BUILTIN/ikeSteep_diffuse
steepTexScale = 1,1
steepTexOffset = 0,0
steepBumpMap = BUILTIN/ikeSteep_nrm
steepBumpMapScale = 1,1
steepBumpMapOffset = 0,0
steepNearTiling = 50
steepTiling = 50
midTex = BUILTIN/MunFloor [Diffuse]
midTexScale = 1,1
midTexOffset = 0,0
midTiling = 90000
midBumpMap = BUILTIN/MunFloor [Normal]
midBumpMapScale = 1,1
midBumpMapOffset = 0,0
midBumpTiling = 90000
lowStart = -1
lowEnd = -1
highStart = 2
highEnd = 2
globalDensity = 1
planetOpacity = 1
oceanFogDistance = 1000

And here's the whole cache:

ModuleManager - Copy.txt

If this is the issue I have no idea how to fix it.

Update:
I'm not really sure what happened here, but I landed on the ground with a Kerbal and this resulted. This was 1.8 KSP with the original rescale mod.

I thought I'd try again since I was pretty bored, and the issue persists.

I completely deleted the rescale mod and wrote the config manually, and although it rescaled properly, the issue still persisted. hopeful for a fix, even though it's been 9 months

For what it's worth, I'm seeing a similar issue in 1.12.4 (to the point that it's not worth me posting screenshots - they'd basically look the same.) Obviously WAY ahead of what SD was written/compiled against, but another point of data for you.

Odd note though - it worked fine for me in 1.10. @K9Advanteaux: If your fresh install of KSP didn't involve deleting the folder entirely and redownloading it from Steam, you might want to try that - I know I've had issues where something weird was cached somewhere unexpected, and it caused an absolute mess with a mod.

Addition - I was troubleshooting this because I really wanted to play with it in 1.12.4, and the steps I followed here in this comment actually fixed things: #96 (comment)

Note that the changes didn't actually fix THAT issue I'd reported (it was my own fault - hence the "delete and redo all your mods" suggestion - but doing the same things did fix this one. I suspect that the "minlevel" for PQS is what fixed it - it makes me wonder if the surface around the KSC is getting unloaded, and then something's going wonky to prevent it from being reloaded.

Also note my comments later on in the bug report - I deleted EVERYTHING in KSP. This means your settings.cfg too - my suspicion is that there was stuff in there that caused issues.

Addition - I was troubleshooting this because I really wanted to play with it in 1.12.4, and the steps I followed here in this comment actually fixed things: #96 (comment)

Note that the changes didn't actually fix THAT issue I'd reported (it was my own fault - hence the "delete and redo all your mods" suggestion - but doing the same things did fix this one. I suspect that the "minlevel" for PQS is what fixed it - it makes me wonder if the surface around the KSC is getting unloaded, and then something's going wonky to prevent it from being reloaded.

Also note my comments later on in the bug report - I deleted EVERYTHING in KSP. This means your settings.cfg too - my suspicion is that there was stuff in there that caused issues.

Hi, apologies for necroposting but I just tried this, and it seems to have stopped that one terrain glitch for me too (yay!). This solution seems to just have entirely deleted the terrain under the KSC though, and now it's floating over the ocean with an island next to it. But at least the terrain stopped being all janky :D

My terrain glitch was similar to the last image K9Advanteux shared in their original post:

Addition - I was troubleshooting this because I really wanted to play with it in 1.12.4, and the steps I followed here in this comment actually fixed things: #96 (comment)
Note that the changes didn't actually fix THAT issue I'd reported (it was my own fault - hence the "delete and redo all your mods" suggestion - but doing the same things did fix this one. I suspect that the "minlevel" for PQS is what fixed it - it makes me wonder if the surface around the KSC is getting unloaded, and then something's going wonky to prevent it from being reloaded.
Also note my comments later on in the bug report - I deleted EVERYTHING in KSP. This means your settings.cfg too - my suspicion is that there was stuff in there that caused issues.

Hi, apologies for necroposting but I just tried this, and it seems to have stopped that one terrain glitch for me too (yay!). This solution seems to just have entirely deleted the terrain under the KSC though, and now it's floating over the ocean with an island next to it. But at least the terrain stopped being all janky :D

Okay, that little island is just the normal peninsula decal, but failing to resize because I did the config wrong lol. I have since learned how to actually edit Kopernicus configs, but it's still an issue. I'm going to try launching from other launchsites which seemingly don't have PQS decals, like Woomerang and see how that works. If it works out, I might just relocate the KSC to somewhere I wouldn't need a FlattenArea decal or PQS mod.

The same issue happens at Woomerang, which I don't believe has any PQS decals. So it only seems to happen to terrain that loads directly underneath a craft. The issue also happens with manually placed decals (through Kerbal Konstructs), but again, it seems this has nothing to with decals. It might be somewhat related to LODs though (just a theory). It would seem the ground directly underneath the craft tries to be rendered at a higher detail since it's closest, but it gets confused due to the unusually scaled planet, and doesn't know what to do.

To replicate this error, all one would have to do is fly directly upwards until the scaled space model takes over. Then let the ship fall back down, and the terrain underneath it will be messed up. The terrain further away will be rendered perfectly fine. This is a common sort of mission for an early career mode playthrough, and this makes it quite odd getting through the early stages of the game.

Sorry for somewhat contradicting what I said a couple days ago lol

I've learned from Starwaster on the KSP/Intercept Discord that editing KSP's settings.cfg to change the "minDistance" will fix this. I've had minDistance set to 3 in the high preset. Unless I create a separate install for SigmaDimensions (I'm using my main KSP directory), Steam just sets it back to 8 automatically :/

Hi there, I'm in the middle of a job change so this might take a while to look at.

I have the bug on my to do list tho, so I hope I can get a look sooner rather than later

Ignore the closing and reopening, it was just a false positive. I'm also going to throw in an @, because frankly I don't know how this works @Sigma88

Sorry, didn't mean to rush you
Real life is 100% more important, so take your time