Who use the shake on fvwm ,please help me !

Apple Shake Interface handle problem!
The problem is the with the window border.If you open a window (shake-file open win) over the shake interface the border starts vibrating, if you put the cursor over the border its vibrating between your setting and the shakes default (windoze like) pointer. This effect makes 100% load of CPU.If You shading up the background window the smaller (shake-file open win) window border works normally. Thank you for Your help!
What do you think this problem!