It usually starts doing this after a few weeks or months of regular uninterrupted use. Considering this app is used by professional musicians to perform in front of audiences of thousands of fans, having the possibility of the app crashing hard at a random time hanging over you is a pretty powerful disincentive against piracy.
Over the years, many cracking groups have tried and failed to overcome this. The guys at ableton are extraordinary programmers and they've obviously done a number on this one.
There were even rumours that one of the top audio software cracking group members was actually an ableton developer, and that they leaked these devilishly broken builds to the warez scene themselves.