backpedaling binding | Street Bike, Biking Boards

Campagnolo 11spd Potenza

When within the stand all the pieces works superb, the bikes shifts up and down, chain runs true and it coasts and backpedals easily. However after I’m using it backpedaling turns into a difficulty. It shifts up and down and coasts superb but when I backpedal the chain goes slack and the derailleur begins binding. I attempted opening up the hole between the higher jockey wheel and the cassette, as it appears that evidently the backpedaling motion is dragging the jockey wheel into the cassette, however that did not assist.
It binds through the whole cassette, extra so within the bigger cogs.

I eliminated the derailleur from the dropout however left it hanging on the chain and did a fast test and the dropout seemed straight. Earlier than I take away the chain and derailleur from the bike and do a more in-depth test of the hanger is there anything I could also be lacking?