after i placed FEL and rejoined world my game crashes
https://pastebin.com/wYQsX7Bf

If my MC Deobfuscation mappings are correct, isOutsideBuildHeight() is throwing an exception because somehow, the block position is being put in an impossible location, and thus, returning a null value. This is a NullPointerException.
Vanilla code returning the null value:

What could be causing it:

Y-position value is somehow below 0, or above 255

ffgeuaInit() is creating a blockpos that it should not. Have it check y-values before returning the BlockPos object.