Good morning, I also have the same problem, the plugin changes the flag but does not translate.
I tried removing it from the menu and setting it “floating” it starts working again. I will preface this by saying that I have had the flags in the menu for over 3 years and have never had a problem.
I would like everything to go back to working as before. I await your guidance on how to get the flags in the menu working again.
My website is https://autoluserte.ch
Thank you