Do you mean that the hyrdaulics are moving the auger around when you aren't moving the switch? Or do you mean that the hydraulics a seeping and letting the auger move after a while.
We have a 2388 that seems to have oil leaking past in the cylinder or something. The auger will settle back towards the combine if it is out, and out of the stopper if it is in. I believe you can make it not go out by adjusting the little carrier wheel where the stopper is. Get the auger to over-center so gravity holds it in.
I always tell the operaters to put the unloader switch to the in postion and leave it. If the limit switch's are working properly,if you have a hyd leak it will go ahead and correct itself. CIH had problems with the auger falling off the saddle on older 1600's but that was a poppet problem that you could cure by grinding some off the poppet don't rember how much. Might be some debris in the vavle stack keeping it open. Let me know what you come up with.