I was able to get to a level 3 castle and then I clicked off of the game for a second and it crashed. But other times it did just crash randomly.
It does have a few small usability issues. For example, it took me a bit to figure out that I have to deselect the building tile to be able to click on the training building to make a unit. Also, when you click on a unit that you've made it selects the unit and it also opens up the training menu that you have to close. And then the buttons weren't working so I had to use the hotkeys for each button every time (not sure if that was intentional or not).
Either way, I think it's still fun and has some potential. It does feel a bit buggy, but that's to be expected in a game jam.