Here is the mod in question https://www.curseforge.com/minecraft/mc-mods/pistronics-2
Pistronics is mod a which adds modular pistons and rotators.
Though it is the kind of mod which may introduce weird behaviour with other mods, it worked with a lot of tech mods like Buildcraft or IC2 even when moving or rotating unmovable blocks.
Sadly GregTech is another matter. Some blocks added by GregTech work (e.g. the building blocks). Other blocks turn into the generic variant of that block (e.g. when you rotate or move a block of copper ore it turns into and unknown ore). And all the machines and cables just disappear leaving behind a ghost block of sorts. Due to the nature of how GregTech is implemented this behaviour probably can not be fixed, but I thought that I’ll just let you know anyways. At least it doesn’t crash the game 
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Yep, cannot be fixed, I have no actual control over the way the Mod moves Stuff.
Actually GregTech is one of the more easily moveable mods, if the mod just updates the block ID’s, transfers the TE NBT data, and updates the coordinates (which is what should be done) then it should generally ‘just work’. I’m guessing that mod is special casing things instead of just doing it correctly.
Do you have the link to github or so for it’s source so I can check it out?
That actually is the Issue that causes this. GT6 Blocks do NOT spawn a TileEntity because they literally cannot do that, so the TileEntity after a setBlock is null, and cannot receive TE NBT Data.
Yep, looked at the Code, not all that surprising that it doesn’t work. It’s a wonder it does not crash due to Class Casts at some points.