Intermittant flash / lose connection on external monitor

Macbook Air 13 early 2015 - Monitor: Dell P2418D. It's running 2560x1440 60hz native res, on a DisplayPort connection.

Whenever I use a Mini Displayport > Displayport cable, the monitor flashes intermittantly. I couldn't get my head around it because it was very random, but now I think I have managed to isolate the problem to a power supply issue. Whenever it feeds ground - something loses connection. In the sample video there is only a touch of the magsafe to the body, and the monitor has to reconnect. (link: http://skrift.nu/wp-content/uploads/2019/12/59662927285__C018F931-085F-4B1F-A1ED-7139F2193E5C.mov)

I am testing out starting with upgrading the cable to a Mini DisplayPort > Displayport Female adapter to see if the port has something to do with it.

Any ideas? How is the graphics/power supply inside a macbook air - can this be short circuiting?

Cable quality? Monitor fault?

Please help?

Cheers/

mkdmp