Yeah, I see what you mean. But it is not the syncing that's the issue, that works fine.
When I have a track (gpx 1.1 file with trk, trkseg, trkpt xml-tags) I can upload it in MRA Routeplanner on PC as Route-track and as Tracklog.
In the MRA-app with Navigation on my smartphone I can select Routes & Tracklogs and the track can be seen under 2 tabs: Routes or Tracklogs. The track can appear in both lists depending on being uploaded as Route-track or as Tracklog.
However, when my smartphone has no internet connection anymore, the Tracklogs list gets empty on Android 9 but remains available on Android 11. This is a bug i.m.o.: instead of showing 'No internet' in the Tracklogs list, show the tracklogs.
So this also gives a solution: import the track as Route-track, not as Tracklog.