Can't update design for blocks
I have the similiar issues. I don't know exactly what the problem is, since I should have been able to update some sites. But I have serious problems with updating the display of my Page list block.
If somebody solved this please report!
First when I tried your approach it didn't work. Since you said it worked like a charm I knew there needs to be something blocking me from working it.
I knew I had installed the new Multilingual addon which worked for 5.4.2 versions and newer only so I assumed this could be the problem. I unistalled the addon and then, auch...my sites was having problems redirecting to the correct language site. Tryed php forwarding, didn't work. Then I made a custom page type that was forwarding to my first language site, activated it via my theme, applied it to the Home page and the links worked again. Whuu...!
So I now tried your approach for downgrading, renaming the directories again and it worked :) Wuhu! The block display updates now also work without a problem.
Thanks again @hawkman and @12345j!
I hope my situation will also be helpfull to somebody, until the concrete5 team will give us a better update.