logically, if the prores looks fine in AE but you export to XDCam and it immediately creates issues, the problem is basically XDCam as a codec, both for exporting and importing.
I would try one last thing before submitting a bug report to rule out any possible prores issues.
1. render out the original prores into a test 30 frame PNG sequence.
2. handbrake the audio to uncompressed PCM wave.
3. combine the PNG sequence and PCM wave file together in AE or premiere and render out to XDCAM to see any issues.