the video image on the monitor is generated by the nav unit. flickering can be due to internal issues with the nav unit, or wiring issues.

the radio cutting in and out is more of a radio issue, or, can as well be part of wiring issue

thus, there could be two separate issues, the nav comp flickering, and radio cutting in/out, or, the wirinig can be culprit...

a proper troubleshooting is of paramount importance - to do the troubleshooting without tearing half of the car aprat, you should try to replicate the issue under various conditions, and note the conditions (write them down)
- does screen flicker in unison with radio in/out?
- does flicker happen before? or after the radio is out?
- does screen flicker when you hit a bump on a road?
- does radio cut in/out with the bumps on the road?
- does it matter if the car is cold? or hot?
- does AC interfere with any of those symptoms? (AC wiring runs in close proximity to monitor wires iin the dash)?
- do symptoms show when the engine is not running (but key is in ACC position)?
- when you knead the wires at the radio module in the trunk, does it change anything?
- when you knead the wires at the nav computer in the left side pocket, does it change anything?
- is there any evidence of moisture in the side pockets? moisture in the battery tub where the radio is located?

once you get your basics covered, then you might want to contact Baris and he will tell you if will take your case or not...

check

carphonics.co.uk

There are head unit units that are plug and play but not with a DSP system.

Sorry, misinfo. I am running my APPRADIO3 through DSP wonderfully.

I extended the MID wires, to move it to the glove & moved the CD player to the cubby where the amp is cd changer would be & attached four wires from the CD changer harness to the cd player.

I found the wire #s here:
Installing aftermarket HU in BMW retaining DSP amp. - YouTube

A fourth is needed to keep it from shutting off after 15 minutes I think #6