Hi there, a while ago i repaired a 16:9 monitor and it hat the same flickering like you mentioned!
The problem whas the flatcable connector on the mainboard inside the housing.
I removed the connector and start to solder the pins again with verry thin wires!
With the first test it whas flickering sometimes (mostly when i whas driving on a bad road), i opened it up again and there whas a short circuit on 2 wires, after repairing the problem wires, the screen never flickered again!

Im not saying that this is also your problem but its just a little effort to check the flatcable!

Regards

Joël