Once you press play button, all the controls will stop working but you can still reset by 'R'. If it's not the case, can you report it more specifically?
In the middle of me playing, clicking on the commands and undoing commands just wouldn't work, It didn't give any signs of anything going wrong it just stopped
I'll try again tommorow my laptop dies and I don't have a charger atm, but I do believe that I managed to make it happen again, and from what I can remember there was no similarities between the two times it happened. My current theory is it's just webgl being a pain in the butt
