Two people reported a very similar crash on starting the game today. I manage to narrow it down to the save game getting corrupt so tonight I replaced the save game stuff with something completely different. I've tested it out here an so far it's working - so I've made that build live. Let me know if you get any issues.
One thing became apparent to me when testing the game and that's when I add in a new level I want to get to that level quickly having already been through the rest many times so for while the game is in early access I've added in a keypress that allows you to skip levels. If you press 'N' on your keyboard at any time it will take you to the next level.
Enjoy and let me know if you get any issues!