The general behaviour is that Magic Fang, Greater Magic Fang and Claws of the Savage do work on gloves, gauntlets, and not bracers.
If you have a screenshot of the property not applying to gloves after casting, post it along with the combat log.
Claws of the Savage wont apply the additional damage to a polymorphed form, but the enhancement should still be there.
While it's possible when different glove enhancement spells are used there might be some variant priority loading? 9/10 times when someone says "magic fang" didn't work, they didn't take into account their adjusted size category after shifting, or didn't calculate their AB correctly. Without any further information it's difficult to conclude if there is a bug.
Certainly, it's not replicatable on my end with a level 19 druid, everything is working fine.