Question about signal and groove~

I follow the instructions here (http://youtu.be/_Uol1_8viDs) to remove the click of groove~, and it works fine when I use rslider to change the max and min position for groove~. But when I send the signals from line~ to groove~ to play the buffer, it still makes clicks when new message in line~ format is sent to line~ to control the playback speed of groove~. Besides, the click also happens when line~ goes to 0.

I have no idea how it happens. I thought line~ can trigger groove~ without clicks.
Any idea ?

Thanks.