OCSR doesn't send Trying (sometimes)

Hello,

I run OCSR SCZ9.2p5, KVM edition. The sipd load is less than 3% (show sipd status).

The OCSR processes 80 CAPS. I have a pcap log that covers 2 minutes interval, i.e. 9500 call attempts. I noticed that 30% of calls do not have 100 Trying. Unfortunately the upstream device needs the it.

Is there any reason for this behavior? Does 100 Trying have a lower priority and can be omitted?

There's no time pattern like Tryings are omitted in the Busy hours etc.

Thank you,

Petr