Whenever you have a network path trough which QoS traffic shall be forwarded, then, all the nodes in the network ought to have proper configuration and bandwidth to be able to forward such traffic.

In this case the end computer received the video traffic with issues, not enough quality.

As you can see in the picture, the QoS is properly implemented in the device, nevertheless, in the statistics it is reflected that the QoS queue is dropping packets:

In that information, you can see that the policy is having lots of discards, so is a good point to start verification.