GUI.repeatbutton crazy?

My game has a repeatbutton which acts as a power regenerator while it's being pressed. It works fine when I press it, with the powerbar increasing as it should. Problem is that I can't seem to move the mouse while pressing the button, as it will reset the powerbar and resend the pressed state. Is there any way to make this work or is it a known bug?

known bug (but not reported probably). see also RepeatButton Behavior: Mouse move releases button? - Questions & Answers - Unity Discussions