I just got 2 client crashes in a row while using a builder block in order to tear down a bunch of abstruse platforms (painted with EnderIO quite clear glass) with a builder block from RFTools.

crash report: https://gist.github.com/TomyLobo/fd70d617f704e9b2638bb29e2a94e83b

Just in case this isn't as 100% reproducible as it seems to me, I still have the shape cards I used in order to make the shape and cut off a side:

1. Shape Card, Shape Top Dome, Dimension 31,31,31 Offset -3,0,4
2. paint everything with EnderIO quite clear glass, at least on the side the next step is going to cut off (I think it was the western side)
3. Clearing Quarry, Shape Solid Box, Dimension 2,7,13 Offset -17,3,4

_{Yes, sorry this was with OptiFine, but since OptiFine isn't anywhere in the stack traces and it takes me ages to start this modpack, I'm not going to reproduce the crash without OptiFine, at least not until I get a new PC :)}

yeah I figured Optfine might not necessarily be in the stacktrace :)

On your note about optifine not being in the stacktraces, remember that they edit base classes (idk if they still do or not these days but im pretty sure they do) so vanilla classes in the stacktrace could really be optifine's doing. But that doesn't necessarily mean that they were the true cause here. Someone else can look into that :P

I got the same crash with no builder involved.
This one happened right when I loaded another dimension containing lots of the blocks mentioned in the OP.

My suggestion: Add a null check, or even a type check.
Right now the Block is type-checked, but the TileEntity isn't.

This issue is stale because it has been open for a while with no activity. Remove stale label or comment or this will be closed soon.

ok so the entire FakeBlockAccess thing from the stacktrace seems to be gone now, if GitHub search can be believed:
https://github.com/Vazkii/Botania/search?q=FakeBlockAccess&unscoped_q=FakeBlockAccess
If you can confirm this was actually removed, you can close this issue since it probably doesn't occur anymore.
Last time I played Botania I didn't use abstruse platforms or had EnderIO installed, so I can neither confirm nor deny :)

ok so the stale bot tells me to comment, I comment, the stale bot closes it anyway.
I think this bot is broken.