Yeah, definitely start over.
In fact, if you get 20-8-like records 3 times in a row, I'd call it quits completely for that suspect round. And by "completely", I mean no more alts (or all your next alts for that round will go 20-8, too).
I'm going 13-5 right now, and my dreams of getting reqs for OU for the first time are officially in the toilet given that my Gen 9 OU GXEs for both my alt and main are already similar, and I'm peaking out at 1500s right now. Not to mention that low ladder is already half-filled with decent teams piloted decently that I lose against with the same team that got me to 1500s in the first place.