Mac Big Sur 11.5 - safari disables add new post in WP

[waltersphoto]

So I dutifully installed Big Sur 11.5 on Friday as I have had no issues thus far with any Mac OS on my iMac
At the weekend I could not add a post or a page to my Wordpress website.
I checked in with my web designer who can add posts and pages using an older version.
I can add using Edge on a PC and `I can add using Firefox on my iMac (that I have downloaded especially)
So is this an issue with Big Sur 11.5 and an update included to Safari and is there a fix?
All I get is a bit of a flash and then a plain white screen
(Oddly I can add to a different website that is older using a more basic theme)

 

[saudor]

Which theme? I noticed major changes in WP recently and didnt even recognize my sites when I wanted to change some widget code.

 

[waltersphoto]

I can t answer that one I'm afraid but it is using elementor.
this is the website if you might recognise how it was built (I assume I'm allowed to post that if not just tell me)