Using a mantle animation from the pack that was free a week ago, the Orca Games Anim pack. Assigned it to the mannequin skeleton and enabled root motion only for it not to work. Have tried every option in the Root Motion Root Lock, as well as checked force root lock. Nothing changes.
I don’t know the “correct” way to do this, but you could try to retarget it onto the same skeleton just to see if the retargeting editor lets you adjust some things there.
Alternately, you could get really cheesy and copy the animation onto your desktop and then try to reimport it into Unreal from there. I believe the import settings also let you adjust the location of the character a bit, but that is a real stretch.