I think I found a better stamina exploit - done it once by accident, not repeated yet.

So on the weekend, I had the game up in the morning. It went past the "refresh" hour (8 AM UTC?) where it changes the daily mission quest requirement, but not resetting all quests. I tried to do yesterday's daily quest (purple dragons). Communication error.

Can't recall if I said retry or not. Maybe not?

Tried the Purple Dragon quest again. Communication error. Think I did no to retry.

Did a refresh of the game to load the day's daily quest. My stamina was 160 higher (2x 80 Stamina attempts not run, but refunded?) than before - I was about 120 over my max. I was able to spend all of the stamina so it wasn't a display error.

Was on Firefox on the .com version if anyone wants to try and replicate it.