I run recently in a strange issue:

I play a updated/modified version of Modern Skyblock 2 for 1.12.1. If I try to visit and come back from "The Beneath", part of my base goes crazy:

AE2 or better Applied-Llamagistics cables disappear or more: I hear breaking sounds and then some of them are gone. Further more the Big-Reactor (Extreme Reactor) structure is stuck and I can't access the Controller anymore.

The only message I could figure out so far is this output from my console:
[12:33:48] [JM-task-8/ERROR] [AE2:C]: BlockState does not contain DriveSlotsState. THIS IS NOT NORMAL. BlockState supplied is of type pl.asie.foamfix.common.FoamyExtendedBlockState.
[12:33:48] [JM-task-8/ERROR] [AE2:C]: appliedenergistics2:drive

I post my full log here.

Minecraft 1.12.1
Forge: 14.22.0.2467
FoamFix: 0.8.1-1.12

It might be mentioned that I'm wrong here or there is something else the cause of it, but I can't tell why it might happen. If it is no issue on your end, I close this and reopen it over in Applied-Llamagistics.

I'm sorry for any inconvenience

I tried re-enable fasterPropertyComparisons and load the same world, it crashed with same IllegalArgumentException.
I will try to reproduce it in a clean install with foamfix and botania only. I could not reproduce it.

Hm, fasterPropertyComparisons? Does smallPropertyStorage not affect it? Could you try FoamFix 0.9.3, as I have changed some related code?

I tried with "fasterPropertyComparisons=false" and "smallPropertyStorage=true", it also crashed with same exception.
I will try FoamFix 0.9.3. With both options enabled, it crashed with same exception. Crashlog: pastebin

With both options disabled, FoamFix 0.9.3, the world still crashes with same exception.
I then reverted back to FoamFix 0.9.1, the wolrd loads normally. (both options disabled)

This may sound weird, but try loading the world without FoamFix, but by restarting the game a few times. 0.9.1 and 0.9.3 are identical except for changes in the two options.

I tried

1. Without FoamFix, the world crashed.
2. With FoamFix, both options enabled, the world crashed.
3. With FoamFix 0.9.1, both options disabled, the world did not crash.

Sorry, this seems to be a issue caused by other mods. and FoamFix helped in a certain setup.

3 not crashing is a coincidence and not attributable to FoamFix, I think.

After removing the issue causing ManaPool from the world while using FoamFix 0.9.1(both options disabled), i switched to FoamFix 0.9.3(both options enabled), i tried placing the ManaPool down and re-enter the world, nothing happens, the world loads normally. I then went to the Nether, noticing my normal world chunks are unloaded, i used FTBUtiltes command to teleport back to my normal world base, the crash happens again with same exception.
It's like the tileentity is accessing its blockstate before its properly loaded.

I got a similar/same issue with block states.
I was loading a singleplayer world then it crashed.
Crashlog: pastebin
After disabling both block states related options(fasterPropertyComparisons and smallPropertyStorage) in foamfix config, the world loads normally.

That crashlog doesn't even implicate FoamFix, though?

at net.minecraft.block.state.BlockStateContainer$StateImplementation.func_177229_b(BlockStateContainer.java:209)

I don't touch this method. Is the crash reproducible with FoamFix only?

I re-added foamfix and it seems to work... but I'm now always (with or without foamfix) not to 100% if it happens again or why it happened... strange.
(Even some of the weird Lightning issues [Shadows and Lights] appear)

Some things still seem to work strange... TiC's Smeltery needed to broken and replaced to accept a new Fuel source (Tank replacement didn't work), Integrated Dynamics doesn't react... (and it seem to happen also with the Nether (?!?))

I can confirm, there is still some issues. Cable (Mekanism) and Integrated Dynamics structures stop working.

Does the same issue happen with the non-Llamagistics AE2?

Can you reproduce it without Foamfix?

I was now only able to test it without Foamfix because if I tried to replace Llamagistics with the original AE2 i run in some issues with Sona core and some other mods.

But this was already pretty informative because the issue of the breaking Cables or Jammed Extreme Reactor Controller is not happening.
It all worked fine even after trying to leaving and entering the "The Beneath" multiply times (I tested it 3 times)

The line of the marked error above changed:
[13:54:35] [JM-task-4/ERROR] [AE2:C]: BlockState does not contain DriveSlotsState. THIS IS NOT NORMAL. BlockState supplied is of type net.minecraftforge.common.property.ExtendedBlockState$ExtendedStateImplementation.
[13:54:35] [JM-task-4/ERROR] [AE2:C]: appliedenergistics2:drive

Here is the log.

I tested all issues on the same worlds with the same mods. Nothing changes except I removed Foamfix for this one.

Weird. Does it happen again with FoamFix? Anyhow, the AE2 error at least means the same thing and is thus unrelated to FoamFix.