Question mark instead of Smylies in Nextcloud Talk

In Nextcloud Talk question marks are sent instead of smilies.
I have Nextcloud 15.0.6 running on my server.
Does anyone have an idea why?

@copiis, you need to enable 4-byte support if you are using mysql.
This guide tells you how https://docs.nextcloud.com/server/14/admin_manual/configuration_database/mysql_4byte_support.html