I'll chime in on my experience with banding/uniformity issues on OLEDs.
Over the past 2 years, I've owned the following OLEDs:
1 LG 55 B6
2 LG 55 B7A
1 LG 65 B7A
1 LG 65 E8
1 Sony 65 A1E
Of those 6 OLED TVs, only the Sony has exhibited vertical banding and uniformity issues.
The Sony, being one of the most expensive at over $3,500, really is a shocker.
When I first powered on the set, not only was there vertical banding, but there was SEVERE uniformity issues on the left hand side of the screen... kind of like dark blobs. I did a panel refresh overnight and that seemed to have fixed the dark blob issue. The banding is still there so I returned the TV to Amazon.
From my understanding, LG makes the panels for it's own TVs (obviously) and for Sony's. So, any vertical banding/uniformity issues in the LG lineup is going to show up potentially in the Sony lineup.
I really don't understand why there is banding at all on these panels. OLED pixel technology seems to be far superior to LCD/LED backlight/local dimming. Each pixel can be in an on/off state. Why is this even happening?!?