VoIP 911 problems show need for backup and/or testing.
A store in Haskell, Oklahoma had VoIP service. The provider had not set up the 911 address properly, so a 911 call defaulted to a national call center instead of the local PSAP (local emergency center).
That's where a second error occurred. The national call center re-routed the call to Muscogee County, Georgia instead of Muskogee County, Oklahoma.
Not only is Georgia somewhat different from Oklahoma, but those two counties are spelled differently.
In another 911 mishap affecting the same 911 center, AT&T routed some inbound 911 calls to the wrong set of phones, phones that no operators were stationed at. THAT error had nothing to do with VoIP as such, it affected POTS 911 calls as well.
Story is at:
(Note that in Canada *all* 911 VoIP calls go to a National center. The Dominion government thinks this makes things better whereas the opposite is probably true.)