In the past month or two I flip-flopped between EL 3 and 4 for at least 15 times now. This IS a technical issue/bug, as all rules for keeping endorsement have been abided to: giving and getting endorsement, no disconnects etc.
Asking around in game, it shows this is a wide-spread issue. Please investigate.
if you don’t get endorsed enough for a period of time, your endorsement level drops down. This is normal - but you might have a glitch I dont know
The system is simply designed badly. It counts every match against matches you didn’t get endorsements from, regardless whether its even possible for you to receive endorsements.
(And if it wasn’t already obvious, you need to receive endorsements periodically to maintain your endorsement level)
If you group with people who already endorsed you, you cannot be endorsed a second time. You also cannot endorse friends, so if you play with your friends you also cannot be endorsed. Yet in both of these cases the match itself still counts your endorsement level down. It also counts canceled matches against matches you didn’t get endorsements from. Its simply stupidly designed system thrown together with minimum effort.
I advise you not to care about the pile of junk that is the endorsement system.