> Are you saying you have two hard-panned mono tracks that show similar output level
I duplicate a mono track so it's the same volume. One left, one right. I (during live playback) see one track get quieter as it's panned left.
> Have you tried re-importing to Cakewalk or Audacity to confirm the levels are wrong in the file?
Yes. You can easily (visually) see that one side is far quieter, which matches what you hear.
I've tried exporting multiple ways. eg a blank master track, or just setting the output of my tracks to the sound card itself.