guess:
have a look at "system32\DRIVERS\UMDF" is there any other UMDF-Drivers…
clean it all (deinstalation!!), delete the service for “WUDFRd.sys”, install your driver without loadorder.
i’m not really sure but it’s a “gut feeling”
BTW: have you looked at the depends for your DLL on the failed PC’s (e.g. with “Dependency Walker”)