I agree that it is a design issue with the gearing in the first stage feeder. Ultimately I think it needs either a gearing redesign, a one way bearing - or maybe magnetic solution like this one for example GitHub - pure100kim/WinchRack_Type2: WinchRack_Type2 for ERCF buffer
In the meantime my own problems are pretty much solved with 500g weights in the spool centres once they get a bit low - I use this little adaptor to hold them in. 500g AMS Spool weight holder - fix for nearly empty Bambu Lab Spools by Ukdavewood - MakerWorld