We are seeing issue when doing video call on 2.4Ghz. If user roam without making any video call user gets decent roaming but if user is on a video call, roaming just wont happen. User remains connected to the same AP upto 80 -dBM and eventually drops the video call. The signal strength is pretty good everywhere and all the best practises are enabled.
"Before a device is steered to a new AP, the system waits for the latency sensitive voice and video application to end." This line I found in "RF and Roaming optimization" VRD in page 21.
Maybe something to do with client match ?