dahau nvr616-128-4k problems with video jumping

hi guys im new to this forum, I was wondering if you guy could help me with a problem im having. I have a dahau nvr616-128-4k with 35 ip cameras coming back to it via 3 poe switches in various places When viewing the images on the screen the video is jumping, the camera frames rates are set at 25fbs stream 1 and 15fps stream 2. ive tried just viewing a 4 cameras on the screen and still no different to viewing 32. The network card is showing that its receiving around 85 mbs. Im really stuck on what to try next as my first thought was the frame rates were to low. some cameras are worse than others.

many thanks