Problem Exporting OMF for ProTools

Hey everyone, I'm a filmmaker who edits in Premiere and does all my sound editing and sound design in Audition. I'm about to send my most recent project to our sound mixer who works in Avid's ProTools, as I've done many times before, but I'm getting a warning message from Audition after the OMF is complete that I've never seen before. It says:

Clip duration is longer than source.

This OMF might not be compatible with Avid products.

And, as you can imagine, my mixer has not been able to open the OMF in ProTools. Does anyone know what this error message means? For additional detail-- I have tried both Encapsulated and Referenced OMFs, and have had the same result each time.

I've speculated that the "clip duration is longer than source" is referring to a stretched clip. But, I didn't do anything like that in my session as far as I know. So, if anyone has tips on how to search for clips that may have been inadvertently stretched, please let me know.

Also, if anyone has any insight on OMF compatibility moving from Audition to ProTools, that would be a huge help.