Reproduction steps:
1) Open user's attached project
2) Open "LevelScene" scene
3) Play scene
4) Click on donuts and watch console's messages

Expected result:
When clicking on the donuts, the OnPointerDown is invoked on the donut.

Actual result:
When clicking on some of the donuts, the OnPointerDown is invoked on the background and not on the donut.

Workaround:
Make donuts order in layer higher than background.

Note:
On which donuts OnPointerDown is invoked depends on donut's possition in collider.