Hi,
Make sure you are using latest MM version from viewtopic.php?f=30&t=86639&sd=d

Here is one that can influence you observe https://www.ventismedia.com/mantis/view.php?id=18198

Please try to capture this in a debug log (step 4b) and attach the log to a Support Ticket: viewtopic.php?f=30&t=86643

This will help a developer analyze why this happens in your setup.

Yes. I use 320k CBR stereo for everything I receive at a higher rate.

Should both Rip and Convert use the same settings in your setup?

My standard is to rip everything to 320k, CBR and stereo. Rip Audio CD in MM 5.0.2.2519 changes from my mp3 settings to a default of 192k, VBR, joint stereo. A similar problem plagued me with Convert Files and I'm told that has been fixed. Perhaps this is a similar coding issue and will be easy to fix. As with the Convert Files problem, I don't know how to capture one of these random changes.