banding occuring when using the brush or gradient tool

Bug report template:

Issue: 

• Photoshop version: 27.10 & 27.11 Beta
• OS: Windows 11

Steps to reproduce:

1. Use a black/white brush or gradient on a mask

Expected result: A smooth gradient or brush mark
Actual result: Grey banding occurring, looking like a low colour bit-depth is being used (when the image mode is 16-bit).

I tested the same image on multiple versions. I get smooth gradients and brush marks on Release version 27.5 and Beta 27.9, but I see banding when I update to 27.10 and 27.11.
I have checked all my gradient and brush settings and made sure they’re identical between all versions of the apps. I have tried playing with brush spacing, smooth and gradient dithering and classic vs smooth method, but that doesn’t make much of a difference.
I have also tried toggling Use OpenCL on/off in the graphics preferences but it doesn’t help.
I have Use Graphics Processor ticked on, Use OpenCL off, Anti-Alias Guides and Paths on, 30-bit display off and GPU compositing on. My GPU is an RTX 4080.

Finally, this is a different issue, but in 27.11 I was getting occasional flickering of the entire Photoshop window (just a single flicker once in a while). I can log that as a separate bug if needed.