For some reason since the new update (.44) players are randomly having chunk loading issues. This isn't a serverside issue as some players see the chunk and for others the chunk fails to load.
If you go past the chunk it loads but immediately unloads the chunks that was loaded before it, if I move back to the other side of this unrendered chunk the chunks re-appear but the chunk that just rendered dissapears again.
They aren't using Optifine as they removed it when this issue started. They have also tinkered with all the video settings and it still doesn't fix this. Reducing/expanding render distance and simulation distance doesn't fix this either.

To replicate = travel around, seems to affect pre-loaded chunks mainly.

I was having the same issue.

I am also experiencing this issue. It's left some pretty beefy holes in the world.

Can confirm aswell

^To give a good idea of what is going on.^

Same issue occurring here as well.

If anyone finds an update to this I am having a similar issue but it seems to only be random single chunks or a small group of them (3 ish) that arent loading in for people.

i have the same problem not only with all the mods 7 but with normal minecraft . i cant even play any more i even send a support ticked to majong en microsoft but da dont wone give me a anser its bin 30 days ago so A FIX IS WELCOME =-)

Hey. I have been having the same issue but have a bit of a fix
it seems the issue happens when you are loading new chunks. I was able to get around this by preloading the chunks using a mod called chunky. The downsides are it takes a bit and while doing it, server performance tanks, but after it fixes the issue

Could this be related?
https://bugs.mojang.com/browse/MC-245010?jql=project%20%3D%20MC%20AND%20fixVersion%20%3D%20%221.18.1%20Release%20Candidate%202%22

By the looks this was a bug with a candidate version (version 1) fixed in version 2? dont know what version ATM 7 uses though.

wel i I don't care anymore majong and microsoft dont give a crap zo i am not gone play any more

I mean they just released 1.18.2 and mods are migrating over to that version so perhaps its fixed in that version? The ATM team may have to migrate to .2 if this is the case.

Also seeing this on a fresh server and client install of 0.2.45 - random chunks just do not load on client side even with F3+A

As a work-around, following advice from r/allthemods - disabling the 3 Adaptive Performance Tweaks mods on the server side fixes things for me.

Disable the 3 Adaptive Performance Tweaks mods
Just change ".jar" to ".DISABLED" at the end of the file.

these files specifically (under setup/mods):

adaptive_performance_tweaks_core_1.18.1-2.1.1.jar
adaptive_performance_tweaks_gamerules_1.18.1-2.0.0.jar
adaptive_performance_tweaks_player_1.18.1-2.1.1.jar