I am an active player and while I don’t play comp, I do play A LOT of QP. I regularly get at least 3 endorsements per game I play. However today, I wound up leaving a game today with less than 30 secs left in it out of pure frustration (I was healing and my team refused to heed my suggestion to group up before attacking). Immediately afterwards, my endorsement rank went from 4 to 3.
I read that can happen if you’re reported? I’m not sure why I would ever be reported though. I try to be respectful and I rarely leave a game early like I did. Maybe there’s another easy explanation for this but I thought I would post about this as I wasn’t sure if it was a bug or not.
Any help or insight regarding this would be greatly appreciated. 
Same, from 3 to 2… for the second time!
Endorsement levels decay naturally over time, if you’re not endorsed as much as needed. Maintaining level 4, and even more so level 5, requires a lot of endorsements in general. If you don’t receive as many as you did before, your level will go seemingly “randomly”. It just means that maybe you were having a bad day and didn’t give off the same kind of “good vibes” that you usually do, and so you just weren’t endorsed.
Over on console I seem to have many issues regarding decay for whatever reason and random Comp penalties over time of me not playing.
Earlier yesterday I got to endorsement level 4 and got around 30 endorsements by the time I got off and over the course of 10 hours I dropped to level 3.
Near as the same issue of randomly getting on earlier today and got my rank and went to customs for a while with friends to leave and get a notice for a ban.