SIP 500 - Internal Server Error

Hi to all! We have FreePBX, and sometimes we have SIP 500 - Internal Server Error problem.We have log with messages like this,

[2017-01-31 12:12:43] ERROR[19050] res_pjsip/pjsip_options.c: Unable to apply outbound proxy on request to qualify contact sip:[email protected]:5060

Nothing about error, only this. Rebooting Asterisk helps, but not so long.

In community nobody get problem like this, or I have bad search. Please help and sorry for my english.

Current Asterisk Version: 13.13.1

I found post with the same problem, but there is no issue