If you try to build near a trap that has been disabled with a Disarmer, the shadow, if it passes through the trigger area, implies the lemming will get eaten by the trap even though they will build through it without incident.
Find attached pictures of the level "Cloning Vats" from Lemmings Cranium showing this in practice... first the laser trap is disabled, and then the truncated builder shadow is shown in the next two images... the first from the Disarmer just as they finish, and the second from another lemming approaching the disabled trap.
Other skill shadows have not been tested, but I imagine the bug to be common to all projections that approach traps.