The +146 pain reflection is indeed not intended.
Do you have a save from when that combat glitch happened, just before (though it may not be reproducible) or just after (if the host didn't crash)?
If so, please email it/them (or a Dropbox or Google drive link, etc) to supportdos2@larian.com, with a description (or link to this topic).
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 (zipper) Folder'.