Soap dispensers are always a source of service calls for two reasons. First, they fail to open and second, they cause door leaks. Dried up soap in a dispenser usually indicates low spray water pressure rather than a bad dispenser.
For many years, Maytag soap dispensers made servicemen a lot of money. A little rubber seal failed and water leaked into the door on the right hand side. It would drip water on the floor at about the rinse cycle. Many of these are still in use.
Grommet Seal Kit
Prior to this Maytag fun, most dispensers used a bi-metal device to operate the latch. This also created a lot of calls when the bi-metal weakened with age or the wires deteriorated and burned up. Most bi-metal units are gone.
In recent years Whirlpool dispensers have shown a weakness by snapping off the little blue keeper in the dispenser. This fragile ten cent part comes only with the whole $100.00 part. It is an integral piece. With labor this is an expensive repair.
Whirlpool KItchen Aid Soap Dispenser
GE dispensers are known for their complexity and Rube Goldberg style. I hate to get tied into one of those. It is difficult to properly wind up the tension springs. The best technique is to buy all the pieces and start new.
GE Dispenser
GE Dispenser Video