Animation bug/Pose T after retargeting on a new model

Hello ! I buy a Ledge Climbing pack system Unreal Engine: Parkour (Ledge Climbing), its great ! But I have a technical question, and maybe stupid but why when i retarget the animation on a new model, the ledgs animations are brokens ( the basics animations like run and other work wells, and the climb animation work weel too separatly ) ? I just took a 3d character and export his skeleton and mesh in poste T with mixamo and the retargetting work correctly, but when i lunch the play level, the animations of ledges seems " broken or off " and the result is a pose T in some interactions. My question is, if i want to change the model and keep this systeme and animation, how i proceed ?