It has been too long since I looked into an l2 grain tank so this may not apply, but I wonder if your clean grain elevator chain is jumping a tooth causing the entire elevator housing to jump back and forth or side to side. I remember having to move an elevator housing back into position because of a bad chain or bent shaft, but that was so many years ago I can't remember which combine I worked on and exactly what the problem was. Hopefully someone else can be more help. Tom in MN