Plugin issue in combination with Polylang (no categories choosable)

Hi everyone,

I ran into a mysterious problem and can’t find a solution.

We run a blog based on the Themify builder and for multilanguage support we use Polylang.

However, we try to import three different RSS feeds (2 german, 1 english).

The issue:
The two german RSS Feeds work fine and they get their category and language assigned based on the rss feed source, works fine.

The english RSS feed makes problems (even though it’s the same setting). Everytime I run the sync for the english RSS feed, it creates the right language for each post, but it doesn’t assign the choosen category for the posts.
Instead I get an additional language in Polylang (language 27) which doesn’t make any sense.

On a staging site however, it works fine.

The only difference between staging site and live site is php 7.4 (vs. live site 7.3).

Is there any known issue on php7.3 or anything else where someone of you ever had an issue with Polylang and the FeedWordPress?

I run out of ideas, have double checked every setting e.g. and I don’t know why this is happening.

Any ideas appreciated. Thanks!

Julian

The page I need help with: [log in to see the link]