Local AMS person said that the issue arises when you mount the entire base on top of an elevator or bin. Supposedly the signal from the satellites can bounce off of the tin and cause distortion, etc. The cure is to get it away from the elevator, or lay out some wood/canvas underneath of the reciever.

I'm thinking that one cure is going to be to mount the reciever on an REA pole cemented into the ground so it can get up and "see around" the elevator and put the radio up on the elevator.