Please email supportdos2@larian.com, with a save at the start of the game (or a Dropbox or Google drive link, etc), and a description of the missing character and what is wrong with the portraits and names of the others.
Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin 2\PlayerProfiles\<ProfileName>\Savegames' folder. In Windows Explorer you can zip file(s) and folder(s) by right clicking on it/them and selecting 'Send To | Compressed (zipped) Folder'.
A few people have reported this, one saying it helped after they switched who was hosting and didn't use custom tags, and a couple others saying it worked after they made sure they didn't have 2 characters of the same race.