Re: MAQS failure
I think you experienced a product failure, caused by poor storage conditions. I have seen multiple complaints in other groups from maqs ordered on sale that was near the expiration date. I feel that the retailers are not storing them properly. Lord knows that they are exposed to extreme heat when shipped in august as well. Then it sounds like the storage you provided was no better.
The medium containing the acid begins to break down in the heat, releasing the acid. Effects can vary from releasing too much initially upon application (which I attribute queen and brood losses to) to having gassed off enough formic prior to application to do a less than adequate job killing mites (your outcome here).
Hindsight is 20/10, not 20/20...
After the fact, I always know what didn't work.