Incorrect implementation of network drives letter may cause USB drives can not been seen by the restricted users even windows detect it as it was conflicting with the network drive letter. Users used their USB drive at home most likely detected as F: or E:. The only solution is re-mapped all your network drives start from mid range of drive letters (s:-z
then roll down new shortcuts with the domain controller OR every time users call ask them plug in their USB drive then go to computer management remotely connect to their host > disk management to change the letter drive
Anyway research or survey b4 implement anything.
Cheers,
Bee. D Moby