I have spoken to the hosts who have changed settings, better, but still crashing and not updating/saving properly, they say there’s a jquery plugin in that you must have added to enable deprecated code to work on the site, presumably your theme code? https://www.dropbox.com/s/c03792fmpgdxjfp/Screenshot%202021-04-29%20at%2013.21.52.png?dl=0 see screenshot
PS, the option to be notified by email only shows if you edit a comment, not when making it, might need fixing in your support system as not obvious
Update, if you try editing multiple headers, nothing saves, it just hangs, can you give specific instructions for any hosting changes or is the error in your code?