In Safari, I cannot type in the prompt window at any point. It simply won't let me click inside that window.

Hey ​@tomski44 
Just to add to what ​@Trevor.Dennis mentioned. I find using Chrome to be consistently stable.

Cheers

Nate

Is this a new behaviour?  i.e. has it worked previously?

Try a hard page refresh.  On Windows that’s Ctrl F5.  Sorry don’t know with Safari.

I googled, ‘To hard refresh a page in Safari on a Mac, use the shortcut Command + Option + R or hold down the Shift key while clicking the Reload button in the address bar’

Does Safari have an Incognito mode?  That might work.

Is something else open that is steeling focus?

I wonder, could an Ad-blocker cause that?