Slate theme: selected page design not working, C5 bar disappears

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My site is:
http://www.jodeurbrouck.com

As you can see,it's a very simple site built using the Slate theme. I've never seen this problem until recently, and maybe it's tied to recently upgrading to the latest SQL version on my hosting account (I thought I checked all the pages to make sure there were no problems)? I don't know, but I can't figure out how to fix it and it's quite irritating.

If you view the events page:
http://www.jodeurbrouck.com/events/...

You can see the problem immediately. It looks like this page design does not even appear to be using the Slate theme any longer (check out the different footer). When logged into C5, the Edit, Dashboard and Sign Out bar across the top of this page is missing completely. I can only edit the page by going to another page from the nav menu, then going into Dashboard/Sitemap. If I change the Design from within the Sitemap menu, e.g. to a different page type available within the Slate theme, it displays correctly the first time I visit the page, but then it reverts back to this mystery page design again. I have cleared the cache and that didn't help.

Any ideas what's going on or how to fix it?


UPDATE: FIXED!

OK, so apparently I hadn't tried everything before posting. Updated to the latest version of Slate 1.5.3.1. Then also disabled Full Page Caching as I read somewhere that can cause problems. Cleared cache, cleared browser cache - success!