MetaHumans - fingers distorted after retargeting

Hi guys,
I’m retargeting this skeletal animation:

onto the UE MetaHuman female body.

All work fine, animation is fine, but the fingers (maybe not the thumb) are distorted as you can see in picture below.
fingers distorted.PNG.jpg

When I look at the target hand skeleton of the MetaHuman, I see an extra level in the hand called “metacarpal” (1st pic below) which is not present in the source skeleton (2nd pic below).

Could this be the source of the distortion ? If so, how can I link the joints ?
I tried linking the index_01 level of the source to the metcarpal level of target, but it did not really improve.

Found the answer to my problem in this video at 8’08"

Thank you!

Check this video. It solves your problem.