SIPB-751 — SIP line misformed
The SIP proxy tried to parse a control message line. However, the line format is incorrect. Namely, a parameter (quoted string or IPv6 reference) is wrong.
The SIP message line is rejected. If the line is necessary, the request will be rejected, too. Otherwise, the message is passed without the line.
This error is mostly caused by incorrect software on the peer. However, if the line seems reasonably to you, please, report the error to the authors.