Why doesn't Input touch begin (OnInputTouchBegin()) doesn't work properly in 4.18.2 (used to work in 4.17.1)?

Thank you for taking care of that issue!

You are right! I did have the Windows Scaling enabled and after disabling it everything is working fine!
It seems that 4.18 version takes the windows scaling into consideration also when it comes to the editor layout as the editor windows are also affected.

Thanks again!