Can't select posts or pages (#2)

Hi Mailpoet team,

I got the pretty same problem (as mentioned here: https://www.ads-software.com/support/topic/no-posts-or-pages-to-select ) with a singlepage installation. The selection of posts and pages doesn’t display the posts ( https://i.imgur.com/Yt1JjE2.png ). Also the options dialog for inserting a post/page doesn’t show up (dunno if the option is disabled by default, if there is no post selected). Inserting pictures seems to work btw.
Another side effect I noticed, is that the styles manager of mailpoet doesn’t seem to work correctly atm. It’s always selecting the content of the default style (header and footer changes). Also not working currently are my custom social media widgets.

I did my research on my plugins and tried disabling them one by one, which didn’t fix the problem, also i couldn’t find an update of my theme, nor wordpress itself in the meantime. (Last time it was definitely working at my spot was 29. Mar 2016). Also my hoster ensured me by mail, that he didn’t do any changes in the background. Probably I’m missing something here…. otherwise I can’t explain it. In the meantime, I also tried different php versions on my hosting, but that didn’t fix anything.

Would be great to get some supprt on this topic, even as non-premium user, since this behaviour makes Mailpoet unfortuantely useless for me (and I guess it would for anyone, who’s experiencing this).

Thanks in advance

P.S.: I already tried the debug modus of Mailpoet, but there was no error. I’m now trying to find an error with the Plugin “Query Monitor” and will report in, if I find something suspicious.

https://www.ads-software.com/plugins/wysija-newsletters/