Sip_xmit to x.x.x.x:5060 returned -2: Broken pipe


I’m using Asterisk 13.9.1 and at the hangup() the SIP BYE message is not sent out the server because sip_xmit return -2. Googling around I only found occurrences where sip_xmit return -1 but that is not my case.
What value -2 would mean ?

Scheduling destruction of SIP dialog '0A51206C-1@s' in 32000 ms (Method: INVITE)
Reliably Transmitting (no NAT) to
BYE sip: SIP/2.0
Via: SIP/2.0/TCP;branch=z9hG4bK6e50b3a3
Route: <sip:630177104@;lr>,<sip:630177104@;lr>,<sip:;lr>
Max-Forwards: 70
From: <sip:3995555599;;user=phone>;tag=as55a5b7f7
To: <>;tag=s+1+419d0001+634d3545
Call-ID: 0A51206C-1@s
CSeq: 102 BYE
User-Agent: Asterisk PBX 13.9.1
X-Asterisk-HangupCause: Normal Clearing
X-Asterisk-HangupCauseCode: 16
Content-Length: 0

[Jun 21 07:50:10] WARNING[13677][C-00000001]: chan_sip.c:3775 __sip_xmit: sip_xmit of 0x7f0a20006db0 (len 594) to returned -2: Broken pipe