I had the same problem during the event. Â At least three times the game failed to save any of my progress, except for resetting timers for play-a-video bonuses. Â For example, in the waning minutes of the event, I played the Golden Pig Castle, after which I got the 5 stamina for playing a video, and had one last event battle. Â Then I went into the nest and arena, played a video on both GPMs, scrapped a few banner items, and then signed out of the game normally.
I logged back in shortly afterwards with about 10 minutes left in the event, and found that the 10 lucky coins from the Golden Pig Castle and points from the last event battle were gone. Â I was back at 15 stamina, though, and it allowed me to do the castle run again so I got the LC back, but after the run it did not prompt me to play a video for 5 stamina. Â Back in the nest and arena, the items I had scrapped were back, and both GPMs were indicating that a video was available to be played, but the option to play was grayed out and would not come up again until the requisite 12 hours passed.
Fortunately the GPM spins that I lost hadn’t resulted in set items, and the lost stamina didn’t make a difference in my event result, but still it was a bit perplexing to say the least and left me wondering if I had lost other progress that I hadn’t noticed.