What platform does this happen on (Windows, macOS, browser etc.)? And does it happen no matter what creature you have loaded in the editor? Or does it only sometimes happen?
I haven't been able to reproduce this at all. Could you maybe send me the log file after a crash? Here's the path where you can find it on Windows:
C:\Users\<your_username>\AppData\LocalLow\Keiwan Donyagard\Evolution\Player.log
You can find my contact e-mail at keiwando.com/contact