Swann DVR really weird problem losing camera image (NEW)

Here is a rundown of my situation:

- Model Swann DVR8-1580

- Recently purchased it

- Already been replaced under warranty for same issue (after 1 week), so I presume its cables/power supply etc

- I am intermittently losing camera vision randomly on cameras 4-8, sometimes more than one.

- Example: camera 7 goes black (does NOT say no signal)

- PROBLEM IS RESOLVED EVERY TIME BY RESTARTING DVR

- Cameras 1-4 always working

- I have swapped all the power supplies for new ones and interchanged them, no difference

- All wiring tested with multi-meter (no shorts that I can detect)

Would appreciate any advice, Swann has no idea.