this issue seems to be an existing ddts, though its minor,
Symptom:
When a user tries to login over the phone and enters an invalid password, Unity returns with an error message (failsafe) and disconnects the call.
Conditions:
This problem may occur with Unity 4.2(1) and Unity 5.0(1) when the user is set to use a language other than US English. This problem does not occur when user is set to use US English.
you many need a patch to fix this and need to contact TAC