Are you using my mod GM Toolkit - Larger Scenes and More Objects?
Because exactly this kind of issue was reported to me weeks ago:
For instance, one players two handed sword had turned into a one handed (for me it was all still correct though). A mace was a shield, and so on.
It turned out even though the players all had my mod not everyone had the exact same version... though they thought they did (I was updating it very frequently and changing the mod name each time to include the version number - which resulted in Steam thinking this was a new mod each time and littering up their mods folders)
The solution was to clear BOTH these folders
Documents\Larian Studios\Divinity Original Sin 2\Mods
and
Documents\Larian Studios\Divinity Original Sin 2\Local Mods
After that the GM made sure everyone had the exact same version of the mod and then the problem went away for them.
Even if you are not using my specific mod you may want to backup the mods in those folders and then clear the folders and re-subscribe / re-download whatever mods and have your players do the same insuring that everyone has exactly the same copies of everything.
Even if you cleaned up the mods folder do also check the local mods folder.
EDIT - from another thread as well:
I tried many different stuff. What worked in the end is sending the mod files from me to all my players, after I unsubscribed from all.
