When you say full do you mean FULL, if so it maybe that there is'nt enough room for the paddles to move freely and feed consistantly, same happens to vlocitys
I have tried one of these, but didn't get on to well with it, as you know i have & still tried a fue different types of hoppers in my time (understatement), & this happen to me aswell if you fill them up to much... sell it & buy one of these...
It does say in the instructions (It's not the man thing to do but yes i did read the instructions) that you shouldn't turn it on when its loaded with paint. It says you should turn it on and then fill it.
I've been told its something to do with the electronics monitoring for jams by checking the resistance against the motor. When trying to start up loaded the resistance is too high and it thinks there is a jam.