If you're on a server which restarts, after leaving while trying to connect you will receive a 300s timer.
- Legacy ID
Be in a server which is restarting (evidenced by solid yellow chain and later a solid red chain with a message "No message received in x seconds").
Connect to any server.
You will receive a 300s wait timer.
I was told by terrorvictor to report this in this thread on steam (since apparently this is not intended):
Thanks for sending in your feedback on this issue. I'll close the issue as a duplicate of #11456. It was filed later, but for some reason it has received more attention.