vermeer 935i auto feed problem

[matty111]

hi all, i have just purchased a vermeer 935i chipper great machine other than i think there is a fault with the autofeed.
it feeds wood as it should and stops the feed roller when under load but it then wont restart the feed roller unless you press the button on the top of the feed chute.
does anyone know what the problem could be? im thinking maybe speed sensor or somthing

thanks for any help