I’m currently using iPad Pro 2024 13’ with pencil pro. I bought glass protector for the screen and I found this problem too. Every apps I tried have this wobbly line when I slowly draw straight line diagonally. Procreate Artstudio fresco csp you name it, I got most of the painting apps you can have. I searched around found that the thickness between the tip and the screen is the key.
The glass protector is 0.28mm thick and I’m using the original pencil tip. I tested directly on the screen, it got much better, I think only got wobbly because of the hand. During my search I discovered this video down below on YouTube which uploaded 4 years ago. You can translate the subtitle to understand it. But things still not clear of course and I can not sure this is a hardware problem or everyone having it.
I ordered a matt protector with 0.22mm thickness and magnetic on the screen. Don’t know if it works…I got a 0.11mm backup tho…but it sticks on the screen, can’t enjoy the beautiful high resolution screen anymore.
I wonder if the material of the glass protector is the real problem here, although I do read that some people have glass protector still works fine.