This is ultimately an expected (if unintuitive) effect of how the laserer works, but I can see why it might be desirable to change this. I'm going to leave this open for input.
As a refresher on how the Laserer works: Each frame, the lemming looks for terrain starting at the tip of the laser-pointer, and going in a diagonal line. There is a distance limit on how far it will go. Visually, this line is the laser itself. If the laser encounters terrain, a blast occurs at the point where terrain was found; this blast removes terrain. If the laserer fails to remove any terrain (either due to hitting steel / a wrong-direction one way arrow, or due to not finding any terrain within the distance limit) for a certain number of consecutive frames - 10 IIRC, but I might be remembering wrong on the exact number - it reverts to a walker. To be clear, except for the "stop after certain number of no-destruction frames" check, each frame is completely independent of the previous one, and does its own terrain check from scratch.