Chain stays on when rotating the cranks forward or when rotating the wheel backwards, but if I spin the cranks backwards the chain jams between the cassette and the top jockey wheel and then when I spin the crank forwards again it drops the chain on the inside.
No components have been changed?
Bent tooth, front or rear?
twisted chain, broken link?
Bent mech/ hanger?
Double check the crank/BB tightness, with the appropriate tools.