Can't delet marked text in email writer

I can not delete text after i marked it. I also cant delete text after this at all. STRG+A and i cant delet text until i refresh the site, the same with normal mouse marking.
I’am running Nextcloud on a Raspberry Pi3 with apache and nginx as reverse proxy.
How can i fix this?
The only error in logs:

KItinerary binary adapter is not available, can’t extract information

Thank you!

Check the browser console. I suspect this is some javascript error.

Also what combination of versions of Nextcloud and Mail is that?