Could you please send me a log file and/or dump file from a Studio session where this occurs? This will help us track down what is happening. You can view this post How to post a Bug Report if you are unsure where these files are located.
I submitted similar bug over 2 months ago and its still not resolved. Roblox Staff said they were looking into it and would keep us updated back then and its still going on.
I cant use Play testing in Studio without either crashing or waiting 3+ minutes for it to shut down.
I think it is caused by your computer trying to load all the game assets, and when you click stop, you stop the creation of the objects and get rid of the objects. When you perform both the loading and the clearing at the same time (by clicking it fast), your computer probably overloads and it crashes.
Keep in mind this is a very basic explanation of what is going on, but this is likely. I can tell this because when it doesn’t crash, it just takes a long time to load.