nightly build gives weird stripes in 'fit' zoom in darkroom and while zooming

Is there an existing issue for this?

• I checked and did not find my issue in the already reported ones

Describe the bug

stripes on 'uneven' zoom levels like 58% or 117%. (e.g, if zoom is not at exact 25,50,100,200% etc.)

Steps to reproduce

I was drawing a mask on a photo in 'fit' zoom.
when stripes appeared. HQ processing solved it, but when you switch that off again, the stripes reappear.
zoom in and out also showes stripes and squares except at 100% or 25,50,200% etc.

Expected behavior

smooth zoom view

Logfile | Screenshot | Screencast

No response

Commit

No response

Where did you obtain darktable from?

GitHub nightly

darktable version

5.5.0+1079~ge3ca9ad8df

What OS are you using?

Mac

What is the version of your OS?

Tahoe 26.3

Describe your system

Macbook M1, 16 GB

Opencl switched on or off does not make a difference.

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

M1

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

No response

Reproduce the issue in darktable's darkroom using the GitHub nightly on macOS with an M1, especially at fit and uneven zoom levels such as 58% or 117%. Compare normal and HQ processing with OpenCL enabled and disabled; done means zoomed images remain smooth without stripes or squares.