That model has a mechanical dispenser mechanism operated by a cam on the timer. There is no one common failure point AFAIK. Someone would actually need to look into it to see where the trouble with the machanism lies.
I don't know if it will help but you can see exploded parts views of that model at the following link:
LINK >
Roper RUD5000KB1 Exploded Parts Views
JFYI
Dan O.
www.Appliance411.com
The Appliance Information Site
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