[Mr_Cat]

Thanks - I've tried that except for the sharpness - I can't get that display options up. When I open the song (after disabling performance mode) I get a "wheel" with controls, bottom left has undo redo left right - I can't see a gallery icon

So I've

Disabled all optimisations
Disabled >> 1) Ensure night mode is disabled.
Unable to find >> 2) Tap the center of the score to bring up the song overlay, tap the display options icon at the bottom left (looks like a gallery icon), then tap "Sharpness" and ensure that sharpness is disabled.
3.0.10 >> 3) Go to Settings->About and ensure you are running version 3.0.10 of MobileSheetsPro

I checked and the the images are 8 bit colour. I re-saved the images for one song on my computer as 24 bit colour, re imported it and it is fine. I'll try a few other colour counts and see if it's only 8 bit that fails

I've re-enabled the application optimisations and with the 24bit image it is still fine.