Courseplay reversing in bga unloading

[E7O]

Hey,

When i use a tractor to reverse unload in a bga silo i often encounter the problem that my tractor won't move forward after backing up and unloading.

It seems to be a problem when the trailer has a little amount of grass left (it says 0% but actually there is like 8 grass of chaff left in the trailer)
Sometimes when the trailer is successful fully unloaded the tractor is moving out of the bga like he should, only when he is got some small leftovers he isn't moving.

Its not like he is at half or 20%, it really says 7 grass left in the trailer. And when i try to unload it manually it still stays in the trailer.
Is there something i can do about it?

Greets