I was playing Haven:caveblock, and this error occurred when i finished building a reactor 128w 54d 192h, it shows up when i right click on the reactor with all the blocks placed. I have used a builder to place diamonds and fuel rods, also while building i used a builders wand and a building gadget. I'm playing on 1.19.2

can anyone help me please porca madonna

The real issue here is that error not being descriptive, assuming all chunks are loaded, that means there is some parts (fuel rods) floating in the middle of the reactor not connected to the rest of the structure. there are other error messages to tell you that, but this one inadvertently takes precedence over those in these situations.

@RogueLogix I get the same error after using a cut-paste gadget from Building gadgets. I have checked and there are no floating blocks inside. I even filled the reactor with cobble and remove it to make sure there were no invisible blocks. Everything else looks connected and as it should be. Can't figure out what the actual issue is. :/
On 1.20 btw. @RogueLogix

I believe building gadgets can have weird interactions with my multiblock system, particularly cut-paste, will need to do testing on that.