[SOLVED] PointerUp not recognized (multitouch issue)

Hello everyone!
When using one touch only, PointerDown and PointerUp will work perfectly.
But as soon as there is another touch on the screen, PointerUp won't be called when releasing the first touch.
Any ideas why this is happening? How could I fix this issue?
Right now, when I first move the player (UI element 1) and then rotate the camera (UI element 2) at the same time, the player keeps moving even if I release the touch on UI element 1 as long as the second touch is still there.

Many thanks for any hints,
Greetings,
Shu

EDIT:
Solved this by disabling raycast target on the UI elements used for highlighting that are drawn above the UI elements that have the EventTrigger attached.