XP Cap malfunction

I’m unsure of the exact number to hit the cap, but yesterday i went from about 77-86.5. Today i capped from that 86.5-88.7. I should of at least been able to get to 90 today and yet i get capped way before i should of.
I’ve capped out nearly every day until i hit 70, then waited till i got my code then capped out ever since then and never have i ever capped out after 2 levels.