Oh yeah... one day it reset on me - I was at a point I was going to break my long-term record and was on right at midnight and I'm guessing I confused it, IDK. I lost my record breaking streak, but would have about a week or so later anyways. And tomorrow I will be at my record breaking streak again (81), I will not be on at midnight.
I've also reset because I was traveling and somehow got logged off and didn't realize it. So even though I did it, it wasn't tracked (my bad). So maybe double-check you are logged in at those times you get reset?