Faults like lines of dead pixels, Half the screen going black, Terrible flicker etc... everyone I personally know with a DW is on their 3rd or 4th unit.
As for the DWF, The latest firmware fixed the HDR, Only real notable differences between the 2 models now is the G-Sync module being replaced with Freesync Premium Pro and 10Hz lower.
I do think the DW was really beta hardware due to it being the first QD-OLED which is why I never got one.
Ah yeah, there were some with those reports, I think that would have been more down to the panel/initial batches rather than anything specific to the gsync module though tbf.
I'm still on my first from when it was released.