Been having the same issue, awesome softare when it runs though. On my machine the crash is always after I press generate spritesheet and occurs about every 4-5 generations.
It occurs less frequently on my office work computer. My home PC it crashes the standalone version often and that's a 1070ti with AMD Ryzen5 3500, 16GB ram, Windows 10.
Edit: this is with both generators, Modern and Fantasy.