The Wither Builder isn't placing the wither skulls and spawning the wither (the skulls remain stuck in the builder) in a FTB Claimed Chunk, but it works fine in an unclaimed chunk. Also it has a visual bug where the rf bar in the ui is stuck at 4464 rf, but in the panel on the top of the screen (not hwyla, but I can't remember the name) it is full and correct.
Should I make a bug report on FTB Chunks' part?
Industrial Foregoing Version:
industrial-foregoing-1.16.5-3.2.11-55cb112
Titanium Version:
titanium-1.16.5-3.2.8.2

That is correct, sorry for the delay.

Ally [IF] in your allys list, this will allow other players to use IF machines to 'grief' your claims though. (block placer, block breaker ect)