Yesterday I finally upgraded my forum from 1.0.10 to 1.1.3. I downloaded the files from here https://github.com/ElkArte/ElkArte/releases/tag/v1.1.3 and uploaded to my forum. I wasn't able to upgrade, I was redirected to forum/install/upgrade.php but an error was displayed, I don't remember exactly the message, I was a bit hurry, it was something general like "An error has occured, click here to retry" but nothing happend once I clicked the message. Strange is that even in incognito mode I was redirected to upgrade.php without asking for admin login.
In the end I solved using the 1.1.2 files and then update to 1.1.3
hmm... difficult to say anything.
I don't see any syntax error in 1.1.3 upgrade.
And I don't see any change in the upgrade file (just a fix for a could of queries) that could justify such an error (apart from the fact I can't find the any error message similar to that one).
I'll investigate (likely on Monday, today and tomorrow I'm basically off).
I'll do another test and let you know the exact error