Worth a try just for this:
The display driver may send incorrect display timings to the monitor when the refresh
rate is set to 60Hz, resulting in poor image quality. [908729/909942]
I didn't get poor IQ with whatever version introduced this bug, but it did disable the 'Game Mode' on my TV via HDMI due to incorrect timings. Took me a little while to notice something
Crap. No change. Anything over 50hz and it disables game mode
Tried another input - game mode is back, but so too is the damn screen tearing. Odd. Bugger game mode then.