I think you might be missing a few steps.
With your recorded capture in sequencer you’ll see it with all the key frames.
-You’ll need to bake to Animation Sequence by selecting the body in the Sequencer and right clicking and selecting Bake Animation Sequence, chose your destination folder and name the sequence.
-Now select the face and do the same.
-Back in the Sequencer just delete your Metahuman and then re add it.
-Now delete the control rig elements in the sequencer that are under body and face.
-You’ll now need to add the animation tracks to your Body and Face, click the Plus Track button on the Body and in the pop out select animation, from there you will see the Baked animation sequence you created in the first steps.
-Do the same for the Face.
-Now these should play back in the sequencer.
From here if you want to add additional animation on top you’ll need to bake the tracks to control rig, once you have baked the tracks to control rig you’ll then need to add an additive track to be able to add animation on top of what you have already captured.
If you look in this video by Gabriella from Feeding Wolves from around 2minutes in you’ll see what I’m talking about.
Hope this helps.