I have putted two boulder trap in the second level of Deeper Dungeons. If you load the savegame I provide, an Imp will put one, but the other, as you can see, the Imp left the trap crate in the floor and never filled the trap with it. You can see the crate trap just near the boulder, why the Imps didn't bring the crate trap to the boulder?
There isn't any Error or Warning in my log file.
EDIT: I have loaded my savegame executing keeperfx_dbg.exe and I have putted Imps near the crate trap, and looking my log file there was two warnings:
Warning: lights_stats_debug_dump: Wrong global lights counter: 238 static lights and counter says 0.
Warning: lights_stats_debug_dump: Wrong global lights counter: 3 dynamic lights and counter says 0.