Is this the fight after meeting Leandra?
If you email your latest save (or a Dropbox or Google drive link, etc) to supportdos@larian.com, I can try it here. That error often indicates a driver or hardware problem, but maybe if something in particular in that encounter is triggering it, a save after that point would be ok (assuming the issue is not a problem in the save itself).
You can use the report.zip file generated by the
D:OS EE Analysis Tool. Extract the zip file somewhere, run the AnalysisTool.exe, browse to the install folder if it is not automatically detected, optionally run the tests first, and generate a report (it will be saved in the same location as the Analysis Tool).
To reduce the file size, you can delete all but one of the saves from the zip (double click the zip file to open it in Windows Explorer, then browse down to the savegames and savegame_patch folders).
Alternately, you can just send the save: each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin Enhanced Edition\PlayerProfiles\<ProfileName>\Savegames_patch' folder.
You can try disabling texture streaming; that is the main cause of switching textures, though with this triggered by combat, it may be related to the combat UI.
Disabling texture streaming increases memory usage, so could cause stability issues on systems with less than 4GB RAM. This setting can also cause the game to crash on startup, but if it does, it is easy to change back.
Open the graphicSettings.lsx configuration file (in the '..\Documents\Larian Studios\Divinity Original Sin Enhanced Edition' folder) in Wordpad, or other text editor, and search for the term 'Stream'; two lines below that, change the one to a zero to disable texture streaming.
<node id="ConfigEntry">
<attribute id="MapKey" value="
TextureStreamingEnabled" type="22" />
<attribute id="Type" value="0" type="5" />
<attribute id="Value"
value="1" type="4" />
</node>
