thread.join() only works when debugging

I have some code that i am trying to run that works in debugging mode when i have a breakpoint set, but it does not work otherwise. What i believe to be happening is that when i call the thread.join() method, the thread is not ending but it does end when in debugging with a breakpoint.

I think this is a simple solution and i just cant seem to come across the answer and was hoping if someone here can help. I know it seems kind of vague and i can supply more info if necessary

Thank you in advance!