I know whats the problem
If you have a big scene and it causes alot of lag it might say something at the topright corner or if your scene is large but not to large to cause lag it will do the same but if you give it time you could probably save it and restart
Algodoo
I once was making a marble machine named Marble Machine Glass then halfway through build something popped up and said something in the topright corner
but thankfully I was able to save it and finish it and its in algobox so go to my profile.
Wtf all wrong on the tanks on right side overseer has six drones not five!
Necromancer has a whole army of drones not four! Overlord has 8 drones not zero and same for manager! Hybride has two drones not five! 3/10