Games keep breaking, won't simulate when I hit play

This has happened to me multiple times… I’ll work on a project for a while and then at some point the project won’t play anymore. It launches, fails to possess the character… and then I’m stuck floating around like a spectator.
When I click stop it makes a strange noise (not the one it usually makes)

The first time this happened I believe it was because I messed something up in a construction script. But this time I am following a set of tutorials step by step and I don’t see any reason why this would happen.

What are the World Settings? Is it set to use the right pawn class?. I know if you possess another character and you don’t have a collision box around them, the camera willl appear inside the mesh. Are you getting any access none errors?

yes, it’s set to the right classes. There is nothing that should be causing this, and there are no errors.

I’ve looked all over to try to figure out what the sound mean. It plays a similar sound to the normal stop simulation sound but it’s different.

What are the tutorials you followed to cause this issue to occur, do you have a video showing the issue you are having?

this FPS tutorial. After I finish the crouch it seems… like last time this happened it was playing just fine and without changing ANYTHING when I hit play again it was suddenly permanently broken.
This has happened to me while following these tutorials twice and once while I was trying to make my first game (also permanently broken now)
I really want to find out why this is happening so maybe I can recover these games or at least avoid it in the future. I don’t really know how to troubleshoot or even what to search for.

ok, I went ahead and tried again. My game broke again. I don’t know how I’m supposed to make a game if a simple walk/run animation is permanently corrupting my projects.

The animations and model are from MIXAMO.

I hit play, everything was working fine. I hit stop, it made a strange noise… then when I hit play again it failed to possess the player and was permanently broken. Now I was running 4.15 and I’m updating now but that couldn’t possibly be the problem. I want to make games with Unreal Engine but all of my projects keep getting corrupted