Whenever I leave the world, regardless of how I leave it, it will not allow me back in. Here is a walkthrough: 

1. I log onto the world for the first time. Everything is typically fine, no issues. 
2. I save and quit, then close minecraft as a whole. 
3. I open up another application, such as discord. 
4. I reopen minecraft and try to join the world. It is listed under the friends menu, and I am able to click on it. 
5. I recieve a textbox saying 'joining the server' or something similar, and after around 10-30 seconds, i recieve a message saying 'unable to connect to world.'

This does not resolve itself even after restarting my computer. The world host has to close the entire world and reopen it. This is plain awful and infuriating.