Behat testing (for you to run) Apply the patch attached to this issue Run behat for the @mdl59784 tag (sorry, it's deliberately slow) Confirm no failure I'd recommend applying the test patch and running behat on the pre-upgrade site too to demonstrate the fix. Unfortunately it's a semi-random fix so isn't reliable to replicate (yay). Manual testing With the above patch applied, open a course home page and turn editing on Click on the " Add a block " link immediately: Confirm that the page does not redirect Confirm that the dialogue has both a title, and body content Note: There is likely to be a gap between you clicking on the button, and the modal opening. The modal will open, but we felt it better to do this than ignore the click entirely. There may be scope in a future issue to add a loading spinner but in most cases there is only a negligible wait and not the deliberately extended wait because of the testing patch applied here.