Checking the mailbox right after closing it will make the bird flying away sound stay on forever, and it can stack with more birds.
Step 1-get pigeon mail; step 2- check mailbox; step 3- close mail window; step 4- immediately check mailbox again.
It seems its still reseting farm progress everytime you leave/re-enter, but I don't know if its because I planted the beans for the quest or because I used a roadsign, because it was working fine before I did either of those 2 things, I'll check it and edit this.
EDIT: Well, it reset without either of those being a factor, but I refreshed the page and hit continue and the save was after the quest to build a pallet (the wild grass bed).
EDIT2: Seems like the save system is the thing thats messing up here, just checked again and was at the Helter Shelter quest with barely any wood/rocks, and now after completing it and refreshing the page again I have enough wood but still need some rocks. Checked again and its saved it complete, so now I'm gonna complete Back to the primitive and check where it saves.
EDIT3: Yeah it seems like the save system is slow to catch up to where you actually are? Like if you do all the quests in one go and quit, then come back next day only to see the game only saved like the first 3, weirdly enough I still had all the mail I got from completing the other quests, and when those were re-completed the bird didn't show up (not like it was necessary seeing as I already had the mail, but might mean I'm gonna be out of a farmboard again, which kinda sucks).
And now its freezing on "Please wait" after hitting continue, so guess I'll wait for this to be patched before reseting and losing that EXCELLENT first map
10 apple trees and 6 olive trees lost to the void
Also I got some people on the farm board and uh, I think its also picking up people that are playing the challenges, which might also interfere with those?