VVX 1500 Video Call Problem

Hi,

We are using VVX 1500 in our network. But we are having problems for delivering the video for some devices (not all of them)

When the device trying to make a video call just an "X" appears on the screen and nothing more.

As I said we are not facing with this problem on all devices, just a few. But important people are using this.

We had this problem in Version 5.4.5  and 5.5.0.

This is so critical for us, what should we do ?

(All the phones are using the same version at the moment but some of them have the problem)

Thanks.

(Sometimes problem is fixed with restart)