Labels set in New Issue are lost

This particular issue template contains at its end a quick action "forward-slash"+"label "+"tilde"+"bug", similarly as the issue 40903 had in its template label feature request and I wanted to add to it also "email" and "notifications", but as soon as I submitted the issue the labels got lost. I thought it's due to me not having enough privileges, but the test instance of gitlab at GNOME misbehaves in the same way.

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)