I'm trying to insert a Promoted Links web part or app part (doesn't matter which, I get the same result) into the default page of my site.  No problems with inserting and leaving in it's default state, but as soon as I edit the part in any way, the page crashes and can no longer be recovered.  Even creating a blank wiki page and inserting a web part or app part then attempting to edit just the display title for the part results in the same thing.

Has anyone seen this and been able to work out why this is happening and what might be going wrong?