I have not run into this problem myself, however in my editor there are a ton of sound errors of sorts on the debug panel for my converted mod. So far it hasn't caused problems though.
If you want I'll take a stab at fixing for you it but you'll have to upload the mod so I can poke around.
You could try and make a new mod with the same name and then simply copy over your terrain data and objects and such one folder at a time.
That the menu sounds don't work though, that's very strange. I'm wondering if you didn't quite get the meta edit correct. Did you make sure to add "Shared" as a datapack? Did you make sure that all the </node> type entries are properly opened and closed?
