What do you mean by WYSIWYG editor? When I edit a wiki page, I only see the option to change from markdown to rdoc, asciidoc, org.
I am using Gitlab 16.3.1 though. I don’t see any other option to change the editor. Maybe you can show some screenshots? I know in editing files in the project, there is the Web IDE, or by editing a single file that I now have. Prior to this I believe there was some other kind of editor, but never used it. So perhaps in Gitlab 16 and higher it got removed and could explain the lack of interest in the issue on something no longer being used.
I’ve just tested what you wrote in the issue (thx for the screenshot, mine is shown in a different place and didn’t see it the first time around), I cannot replicate your problem with rich text mode and saving it. Or even switching from rich text to markdown, it still keeps all my changes.
Perhaps your issue is related to your gitlab configuration or something, or perhaps you can upgrade to the latest version to see if it fixes it.
The only other difference is I use omnibus version 16.3.1 on a VPS, so without docker. But other than that, basic gitlab.rb config.
I would suggest upgrading to see if the problem goes away, or check/verify your Gitlab configuration is OK and not causing any issues. You may need to report more info in the issue you opened and linked here. Check the log files to see if anything appears there that might be useful. You may wish to add that to your issue linked above, but I don’t see a major bug that is affecting everyone. So either something that has already been resolved in versions higher than yours, or something unique to your configuration with running Gitlab on docker.
Check all your logs in the /var/log/gitlab directory in your container. The browser stuff doesn’t really suggest anything to me. Check your configuration also, and explain exactly what you have configured to run Gitlab in your container, what ports have been allowed to the container, etc.
Sounds to me, that it is something wrong with your install, especially since I can do everything on mine without problems.