daniel,
i noticed that master sr assumes gruu support if ua includes +sip.instance contact param in register request, because contact in 200 ok response contains gruu params.
according to rfc5627 gruu support is indicated by
Supported: gruu
that is, +sip.instance contact param is not enough.
could you fix this by making supported gruu test before adding gruu contact params in 200 ok to register request?
-- juha