@OldeBuick you’re welcome to use the Beta build if you’d like. However, if you’re willing to start fresh, you may want to try first just un/reinstalling the stable browser to see if that helps.
Note that when you go to uninstall the browser in Add or Remove programs in Windows, you’ll be shown a prompt asking whether you want to delete any browser data as well. I would recommend first not checking that box (so that your browser data is retained), uninstalling the browser, then install it again and test to see if the issue persists.
If this does work, then you won’t lose any of the data in your browser when you reinstall. If it does not work – that is, the same screen flashing/closing occurs, then I would try un/reinstalling again, but this time electing to delete the associated browser data as well.