Problems with high speed flash sync. Are the highest shutter speeds electronic?

[Frodo]

I had a photoshoot a couple of days ago shooting a backlit subject and using high speed sync so that I could use a shallow depth of field. Camera is EOS R and flash is Godox AD200 (lens EF 85/1.8)
At high shutter speeds (1/6000 and 1/8000) I have noticeable banding from the flash in the image. No banding visible elsewhere. First image.
The issue is almost invisible at 1/3000. Second image.
I know that the flash pulses rapidly so that it can sync with a focal plane shutter. Are the highest shutter speeds on the R electronic so that such banding would show?
Anyone else experienced this?
Tips for removing the banding would be appreciated. I might try selective blurring in Photohop.
In the future I'll use a neutral density filter in situations like this.

 

[Frodo]

LSX Photog posted earlier about how to prevent this:

EOS R Banding with Strobes: HOW TO FIX

BANDING: If you're experiencing banding when using off camera flash, this is a result of the electronic first curtain shutter that the EOS R shoots with by default. HOW TO CORRECT: 1.) Go to Camera Menus, Page 6, Silent LV shoot. 2.) By default, this is set to Mode 1. Change this to Disable...

www.canonrumors.com

I will use a ND filter next time to reduce the shutter sppeed to a zone where banding isn't an issue.

I'm still working on a fix.

 

[Frodo]

Right, I have a fix that works okay (thanks to: https://fstoppers.com/post-production/learn-how-fix-color-banding-using-just-one-simple-tool-7946)
- Select the area with banding using the magic wand - this worked quite well for this image.
- Create a new layer with the selected area - ctrl J. I removed with the eraser, some parts of the image inadvertently selected by the magic wand
- Go to Image - Mode - 8 bit
- Go to Filter - Filter gallery - Spatter (You won't be able to access the filter gallery if the image is not in 8-bit - so do most of your editing before removing banding)
- Use very low smoothness and play around with the spray radius (should be quite high) until banding is just removed.
- I tidied up a few edges of the selected area with a small soft brush.

I tried a couple of different blurs, but found that spatter worked best.

A crop from the image is below.