Hi Michal. Would be helpful to know the unit calling in to the VCSE or whats your home unit that your using. I do believe the 422 is sent becaue the MIN-SE value in the initial INVITE is less than what is configured on the VCS (SIP Configuration - Minimum Session Refresh Interval). The far end system should ACK this, and retransmit with the MIN-SE time allotted in the 422. You should see another INVITE sent looking for service@vcse.systemvideo if that is the destination your looking for.
Knowing what destination your trying to reach like h323 endpoint or another sip endpoint on your VCS E or your trying to reach your VCS C would be helpful. Devices and SW versions included is also helpful.
Ultimately a diagnostic log taken while the call is failing would be ideal, but thats up to you if you wish to post here.
VR
Patrick