Does the kubel have a mind of its own? Does it chase after infantry that it sees (or are spotted for it) but manage to get away from its suppression? It seems like this happens even if you "set it up" by clicking and dragging to point it in a particular direction. I've lost a few because of this unexpected behavior.
Also when you use the "U" key(reverse) it seems to make kubel do forward donuts, never reverse donuts, just forward ones.