Microsoft has decided that Office customizations should never get run from their actual installed location but from an isolated copy of that installation. This copy gets placed to C:\AppData\Local and is referred to as the Shadow Copy – according to documentation it is 100% safe to remove this folder either at login time or logout time. So if the customer is willing to create a login-script or a logout-script to clean these files (%User%\AppData\Local\Assembly\DL3) that really shouldn’t have any adverse effects
