I think this is an older LNAV issue. Seems like, it has to do with these (I)-waypoints, which I had also reported earlier this year:
Minor LNAV Issue
Yes it is an older issue. If I remember well, after an update of Aerofly FS 2020, or since SID & STAR. Since, this uncomfortable problem haunts my favorite plane like ghosts captain, stalking me till Aerofly FS 4.