So, I was doing my quests for Maleria (I just activated a GA, so I was doing the extra five). I was on the 13th or 14th when there was a 502 error after clicking 'Finish'. It took forever to get the site back (more 502 errors, then completely white pages), and then I get this:

"(Quest reward message) You've completed 17/15 quests today!" The Quests widget also shows this same amount.

I'm using Chrome on a laptop running Windows 10, though I don't know if that's important with this glitch.