German content gets overwritten on english page

Hello,

I have the problem, that content of one language (Gutenberg editor) gets overwritten by the content of another language (same post). This happens at our customer’s site, not at each time the customer safes a post, but sometimes. I use “WP Multilang”.

The theme is by myself. The plugins I use are:

– advanced-cron-manager
– advanced-custom-fields
– all-in-one-wp-security-and-firewall
– block-lab
– custom-post-type-maker
– disable-comments
– disable-gutenberg-blocks
– gt3-photo-video-gallery
– gt3-photo-video-gallery-pro
– post-types-order
– sbgd-wrapper-block
– wp-multilang

Any idea where the problem could be?

Kind Regards
Finn

PS: I also speak German.

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