The problem with XF is that it is developed entirely by developers, with no UI/UX designers on the team. The user experience could be significantly improved if UI/UX designers were involved in the development process.
We just had to replace a few broken youtube links so these are the settings we used:
Quick Find: video=youtube
Regular expression: #\[video=youtube;([a-zA-Z0-9_\-]+)\]http[^\[]+\[/video\]#siU
Replacement String: [media=youtube]\1[/media
We had the same issue a few days ago. It is related to the SSL certificate generated by cPanel which triggers an error (check your DNS records) because if one of them fails then the site loads another cPanel account on the same server. Just make sure that AutoSSL successfully creates all the SSL...