Sodium D2 oddities

[vnp85]

Please forgive me for churning out issues -- some are just questions. As I've seen on the FB group that questions go unnoticed, even when I tag people, you as a developer may have encountered other people facing these same issues.

So I have the following oddity in Sodium D2, I initially thought it's a line detection mishap or just something up with my little Sol'Ex.

I would totally ignore the sodium lines, but hey: a filament in sodium.

• the wings look like they show doppler on the entire hemisphere, like the darkest of the line wasn't the line center. Oddly coincides with the equatorial grid of the Sun.
• the disk shows banding where the wings (only 3 pixels away) don't. Am I seeing some interference?
• for some reason, the poles are brighter - again, interference?

I will try with different ERF filters, but I find this simply so odd.