PJSIP with Internal extensions - 401 unathorized on INVITE message

Using chan_pjsip (no insecure = invite as in chan_sip).

Calling between internal extensions, properly defined in pjsip.conf, there is always a 401 unauthorized after an outgoing INVITE, instead of 100 Trying. This may not look like a significant issue but thee are endpoints that do not accept that, we would like to disable this challenge and have it only during Registration (REGISTER).

In chan_sip, it was possible by having an empty secret (blank) but using chan_pjsip it was not possible to do it this way. Even with a blank secret, there is still a 401 unauthorized challenge.

Any inputs are welcome!

Attached is an example from extension 2222 to extension 3333, where there is a first 401 unauthorized to be followed by an answer in the second INVITE As it was mentioned above, not all endpoints will do that (ex. TIPCon1 endpoint)