Same happened to me today.
With my user script engine (Violentmonkey) completely disabled.
- Submit TOC from Picard
- New release by artist
- Type any release title in first tab
-
Tracklist tab : Track parser : Lines start with a track number ; Lines contain track artists ; Use track artists ; Use track titles
Here you see that it has not taken account your track artists. It has kept the green release artist only everywhere - Click Edit Note tab
Then you can’t submit because red Tracklist tab « You must enter a title and select an artist for every track. » — with or without artist fix after step 4 — despite checking all artists are green.
I have to abandon my release. 
Seems similar to this cause.
Updated some stuff, it was not related to Search→Replace.
☞ c/w MBS-9292