RGB matrix slight flicker issue

[NemoAndrea]

Even with gpio_slowdown, there is still a slight flicker visible on the display on rare occasions. Worse still is that at the centerline of the display a column of pixels has a slight persistent flicker that is not very visible when looking at it directly, but becomes very visible during rapid eye movement (pan).

It is not a big problem for the experience, as it looks fine when looking directly at the display, but a fix should be found for it longterm.

Suggestions on configuration options would be appreciated. The display settings can be found in display.py