Safehome

Hi I have a Veezoom poe camera kit. with 4 cameras. Recently after 6 months its developed an unusual problem. When i preview the footage in multi screen 4x4..occasionally on a daily basis the image of some of the cameras becomes really blurry for a few hours. It happens in the same parts of the time line.. so its somehow recorded that way. when I click into the video the recording is ok. Its only the video in the 4x4 preview window that is blurry. If watching on 32x Fast forward. i can see the image gradually deteriorate to very low res then suddenly snap out of it? Any ideas as to what causes the camera to be blurry when watching the recording in the 4x4 preview window to be blurry? (does the sub stream get recorded or something)