I thought I was getting a game crash. I decided to play through the Jetpack Origins mission. I played up to level 65 then took a break. When I went to resume my game and clicked on the Jetpack Origins mission, the game froze!
You don't have to play 65 levels to reproduce this, just home+click the levels and it still happens. In Firefox it crashes the entire browser (killing the Flash player plugin in the task manager restores things without having to stop Firefox too), in Chrome just the game. After some messing around and patience, I found it was just taking forever to load the mission (like a minute plus). It seems the more levels are completed, the longer it takes to load. There's something terribly sluggish going on here.
P.S. Level 13 (Get the Picture) is impossible!