Users in a small location report that audio calls work Tine, but only one video...

Users in a small location report that audio calls work Tine, but only one video call works before the next one gets a busy signal. Three video conference rooms were recently installed by a third party. The audio and video devices are Cisco endpoints. The site uses video and audio calls, and a network investigation does not show saturation on the link The site is configured with QoS and CoS. All devices are registered on the headquarters Cisco UCM duster. What is the cause of this problem?