@Mainmain Please check Pico CMS for Nextcloud v1.0.0 is out now
Unfortunately still no idea about @segh’s issue… We were trying to debug it on IRC, but no luck. I’ll release Pico CMS for Nextcloud v1.0.1 this weekend that fixes another issue. I’m rather sure this isn’t related to your issue, but you can give it a try nevertheless. Sorry 
I still think it’s an permissions problem, but I couldn’t think of any situation how to cause it and therefore fix it.