Could you please send us the AAF as well as the exported Resolve project at davincihelp (at) blackmagic-design.com? Please let us know which event you have started seeing this issue (and if you have some screenshots as well that would be great).
Did you enable the reel number support on the config page before rendering? The MXFs need to have a valid reel/tape name else it won’t show up in Media Composer’s Media Tool.
If you use the Split and Add (with handles), it will put only the media you need for the conform in the media pool. You can then copy/paste these files to another folder/SAN volume, and then this will do an optimized copy of the selects.