In vanilla factorio, the pipe doesn't have fast-replacable group, so it works properly.
But once some mod adds fast replacable group to the pipe-to-ground, this starts to happen, as the mod failed to add the flag to prevent this problem.
The flag is called "fast-replaceable-no-build-while-moving", and is used in underground belt for example:
Code: Select all
flags = {"placeable-neutral", "player-creation", "fast-replaceable-no-build-while-moving"},