The issue seems to have existed for quite some time, hope this does get some attention as I've had this happen to myself a few times.
Seems like winning a game IIRC does fix this issue, though that of course isn't really a workaround that seems efficient.
A megathread has existed for this exact issue: https://answers.ea.com/t5/Bug-Reports/Megathread-Incorrect-Rank-from-Previous-Season/m-p/8711968/highlight/true#M22778
Though seems to be closed, i haven't read through it completely but maybe some have found a workaround that doesn't require you to win.
They might take note of this soon, at least they think it was because some got RP removed but it's happening at such a large scale that I doubt it's related to that.
Until then, just hang on tight until they release a patch or find a workaround.
