I did as suggested. Uninstalled the Navigraph data, and voila. the flightplan did properly display. So, you are right, it’s fine with the base sim.
However, after reinstalling the latest Navigraph cycle the plan is corrupted again. In this case, the Navigraph Discord might be the proper adressee, but not sure it’s worth the hassle given this is the only plan I had these issues so far. Will think about it.
Thanks a gain for taking your time to isolate the issue.