Secret Collector 3 achievement glitched?

I have all cars, classes R1, R2, R3, and R4. Won’t pop. Anything I can do to fix this?

Have you got all the cars in your garage at the same time, i.e. not sold one to buy the next one?

Yours is the only comment on xboxachievements, saying it might be glitched, so figure it might be something else - game has been out a very long time for only one person to suggest that it might not work. I got it back in the day so unless it won’t work because of an update that has been done, not sure what else to suggest.

Yes, I have all of the cars in my garage right now.

I just know some of the other achievements in this game have glitched for people, namely the secret ones.