2003 Caravan - Driver's Power Seat - Front Riser - not working

In my 2003 Dodge Sport Caravan, the Driver's seat Front Riser has
stopped working. The front riser motor vibrates and makes a growling
sound when I briefly move the front riser switch in the up or down
position, but there is no movement in the linkage or seat. I presume
the switch and motor or working, but don't know what else to try. I
have looked for stuck debris in the linkage but could not find
anything.

There are four motors under the seat.

1 - Seat forward-reverse - works OK.
2 - Recline (up and down) - works OK.
3 - Rear riser - works OK
4 - Front riser - motor growls and vibrates but no movement.

If seat is left in far forward position overnight, sometimes when
moving back to normal position, seat forward-reverse motor growls but
works. Later in the day it moves with normal motor sound.
..
Any help is appreciated as I don't have any warranty on this
component.

Thanks in advance!

(to email replace all x with first letter of my first name.)