When placing multiblocks (like a bed) on top of scaffolding the replace scaffold functionality sometimes displaces part of the multiblock to replace a scaffold.

It's from FC and there's some chat in the logs that should remain private, ping me here or on discord if you need the log (couldn't find anything related quark when I looked though).

The bed was placed on the top right scaffold in this screenshot, player facing towards the right in the screenshot (west)

The bed was placed on the top left scaffold in this screenshot, player facing towards the right in the screenshot (west)