Seeing as it was a roundtrip from MC to start, it will use the same source ID’s available to it so one has to hop they match. What I do is once I have color corrected the timeline in Resolve and rendered the files, I go back to the edit page, highlight the sequence in the timeline tab and export AAD. Not NEW AFF! But AAF. This takes the existing AAF that came in and only changes the pointers to the new media leaving all tracks and VFX In place, even if it could not interpret them. YOu will see that the sequence name will now have (Resolve) added to it.
With the rendered mediafiles in a proper MXF/ folder structure, import the AAF(Resolve) sequence and it should just link up to its own rendered media.
Only on very few occasions where conform was back to camera originals and the chance of changing REEL ID might occur that you need to do a “relink to selected” and ensure that TAPE or SOURCE FILE name is properly selected to match.
Michael