So you have an RMB input and a button, which has an on clicked event?
Do you mean that the RMB input event stops working while hovering over a button.
or
Do you mean that the on clicked event of the button does not work when right clicking?
In either case It’s a bit strange.
I added a button to the viewport with an on clicked event, and also added a RMB input event which prints string. Right clicking for me prints the string every time.
However, the button click event does not work when right clicking, and that is seems to work for you which clicking rapidly is odd.