Character mesh not matching animation pose

I have a basic UE5.2 third-person character setup, where I’ve imported a third-party character skeletal mesh following the correct skeleton and I have retargeted the Manny animations to the new skeletal mesh. In previewing animations, everything looks and works perfectly, however when I set the new skeletal mesh in the BP_thirdpersoncharacter and set up the animBP the mesh will animate but his poses do not match that of the original animations.

In idle he looks like a gunslinger with his arms out wider than normal (not in T Pose) instead of falling by his sides. What am I missing?