OK this is an hard one
You have some sort of blobby noise pattern that cuts your characters…
You can try:
-Set Warping to Forward
-Set ALT Motion Source to the matte itself (use the greyscale image motion instead)
-Frame Interp to Nearest
Alternatively if there is a way to export Motion Vectors out of 3D render for the white blobs making your matte channel, you could try that in a 16 bpc or float project) with Twixtor pro, Vectors In – setting that as the Vectors input in AND I have no idea if this will be PREV or NEXT in your case.