Huawei ascend X2
Sedina a8
I was familiarizing myself with the controls when I used the joysticks.
It seems while going up on the Y axis and pulling down on the X axis your X axis returns to it's default state in the center of the joystick, making you lose control of it until you drag it back down again to which it will repeat.

What joystick are you using?

What device OS version?

Default layout for joystick
Not sure

There are also a lot of free "touchscreen testing" apps, that will illuminate the touch points, demonstrating any inaccuracies in how they're registering, like if the touch is "jumping" to a new location, or if you're encountering a "phantom" touch problem because some other digit is too close to the screen.

A lot of earlier Android devices had terrible problems, and even more recent devices can sometimes have the touch-digitizer come partially disconnected around the outside edge of the screen on one portion, which will cause a lot of strange behaviour (sometimes you can gently press it down around the edges of the screen, to help improve this).