Duplicate Authorization Header during retry

[manzonif]

hi,
I have problems in registering with my sip account. I guess it's due to the fact that, during the second retry, the authorization header is duplicated.

If I register the account through command line, the first attempt fails (Unauthorized)), but the second one has success:

REGISTER sip:sip.messagenet.it SIP/2.0
Via: SIP/2.0/UDP 192.168.1.235:5060;rport;branch=z9hG4bKPj1XrrxOPdbwSIIhBAVvlm.onYEoQnb.aN
Max-Forwards: 70
From: sip:5xxxxxxx@sip.messagenet.it;tag=GaP2SnBihhckA4ohyDt2R3dek70XQYfp
To: sip:5xxxxxxx@sip.messagenet.it
Call-ID: Ijefouh6.ptfvZnlNTC3iklkZbwDutVK
CSeq: 26520 REGISTER
User-Agent: PJSUA v2.6 Linux-4.9.35/armv7l/glibc-2.19
Contact: sip:5xxxxxxx@192.168.1.235:5060;ob
Expires: 300
Allow: PRACK, INVITE, ACK, BYE, CANCEL, UPDATE, INFO, SUBSCRIBE, NOTIFY, REFER, MESSAGE, OPTIONS
Authorization: Digest username="5xxxxxxx", realm="sip.messagenet.it", nonce="WXIeUVlyHSVTcdQn/8lr0/Y/XEvQfkcvbmIEr4Zp0LzGPlrqh3AJKO0D38yA", uri="sip:sip.messagenet.it", response="5decad2161eec4c41905a3f331a778f6", cnonce="6LqUedwnQIrbPBuj1e7D2DzG4q5tO4lh", qop=auth, nc=00000001
Content-Length: 0

--end msg--
17:26:30.996 pjsua_core.c .RX 740 bytes Response msg 200/REGISTER/cseq=26520 (rdata0x74801294) from UDP 212.97.59.76:5060:
SIP/2.0 200 OK
....

With sipster, Authorization header is duplicated and fail:

REGISTER sip:sip.messagenet.it SIP/2.0
Via: SIP/2.0/UDP 192.168.1.235:5060;rport;branch=z9hG4bKPjYYxEtG9OCohuX2BLIegJKjQ0jYQEvK1p
Max-Forwards: 70
From: sip:5xxxxxxx@sip.messagenet.it;tag=lK0GQ-GFUROOYaDh90pOwFAjxyroxYL3
To: sip:5xxxxxxx@sip.messagenet.it
Call-ID: VbmrXY.RblC2vmrYrfQ-xbMEPGKiuIDc
CSeq: 60848 REGISTER
Authorization: digest username="5xxxxxxx", realm="*", nonce="", uri="sip:sip.messagenet.it", response=""
Contact: sip:5xxxxxxx@192.168.1.235:5060;ob
Expires: 300
Allow: PRACK, INVITE, ACK, BYE, CANCEL, UPDATE, INFO, SUBSCRIBE, NOTIFY, REFER, MESSAGE, OPTIONS
Authorization: Digest username="5xxxxxxx", realm="sip.messagenet.it", nonce="WXIx0llyMKZzuh9wmxmiqOlkAiqjPuN5bmIEr4Zp0LzGPlrqh3AJKPHXbNyB", uri="sip:sip.messagenet.it", response="9fad324af9e74f6c497853d8a3288eb8", cnonce="HbQAV56NE4cbzWN8daQfBnP0T37V95Q2", qop=auth, nc=00000001
Content-Length: 0

--end msg--
18:49:44.513 pjsua_core.c .RX 721 bytes Response msg 401/REGISTER/cseq=60848 (rdata0x73501294) from UDP 212.97.59.76:5060:
SIP/2.0 401 Unauthorized

Any idea to fix the problem?

Thanks