If you rename any mob from a mod with a name tag. It will cause another name tag to spawn when you look at the mob. Im guessing that's that vanilla tag showing up. I noticed when naming vanilla mobs that this does not happen. in addition mobs that add names to the mobs (Eldritch mobs for example) cause the double name tag as well. I had to disable the titles in that mod to stop it. but there is no way to do that for nametags

one showing a mods mob

and a vanilla one (the pig is vanilla it just looks different do to a mod)

nameplate-1.0.10.zip
Does this fix the issue?

nameplate-1.0.10.zip
Does this fix the issue?

I have tried using the updated 1.0.10 version you have provided, but the problem persists

This is pretty sure fixed with the latest update, reopen if still exist