Animation montage glitches

I am using this blueprint to play a simple animation montage for rolling, in the GASP project.

The animation gets retargeted to UEFN_Mannequin correctly, is root motion with blend in/out set to 0, and seems to be ok when played in the montage panel, but it throws weird movement glitches when tested in-game:

Does anybody know what causes this, or a possible fix?