It seems that building and crates "close" to the "Binary Bridge" (last level available) leads to some problems with the path-finding.
Buildings are not constructed/Crates moved and Hexters flash what i presume is the "no Path" symbol (white spline with red x).
"Close" to Binary Bridge: seems to be the segment which still has "earth" (and you can place buildings) but has persumably the beginning of the bridges-ramp beneath.
How to reproduce:
building : Place building in described position, watch a bunch of confused hexters gather.
Crates: I am not sure how the crates got there, either from trying to reach the building or one on the other side, and aborting the building.