Weekend quests should not be unlimited, so you're definitely having a problem here. But I think it might be specific to you since I was able to do a quest and had my count go up correctly.

Before you do a full 15 quests, does the quest count go up correctly? That is, does it go 1/15 and then 2/15 and so on, or does it always stay at 0/15 no matter what?

Have you only been doing Pete's quests? Have you had this problem with other quest givers?

Please don't do any more Pete's quests for now, as it can be considered glitch abuse.

Just to be absolutely clear, does that mean:

It counts 1/15, then 2/15, all the way up to 15/15, but still lets you do another quest, and then you end up at 0/15 ?

Or do you mean: It counts 1/15, then 2/15, and then 14/15 and then 0/15 (instead of 15/15)

I've asked a UA to open a ticket with you to help figure out what's going on, since our logs are showing something different too.

I hope it is resolved for you, and if I need to fix any coding glitches I'll definitely get involved again. :)