Credit roll back, help please.

I was almost a colonel grade 3 (15k away from ranking up), when my credits rolled back down to colonel grade 1. What the hell is going on!?

Do I get them back due to the credit cap being hit by custom challenges?

Yeah it happened to me a lot you can only earn the limited Cr cap even if you get like 1 mill credit, and you don’t earn the credit you lost you need to earn it again or do it again on the next day.