Hard to tell from that picture, but if the jar is sitting on top of the transducers, you're not going to get much ultrasonic cleaning action. Additionally, the jar itself may dampen some of the action, even if not on a transducer. Pull that out of your ultrasonic cleaner, put a piece of foil in just the water in the cleaner, and run it. It should eat through the foil (no need to let it finish, just look for little holes to form with it dipped in there). Repeat the experiment with a jar and water and foil. That's a good way to make sure you're not just spinning wheels. Normally there are little baskets with standoffs to prevent items from directly sitting on transducers, or overhead fixtures on larger units that allow suspending the item in the tank with wire.
Also, definitely used distilled, ultrasonic cleaners work through cavitation and the minerals in tap water make it less effective, in addition to all of the molecular/atomic interactions that mineral/contaminate binding prevents. Pre-warm the distilled water, and run a 10 minute cycle before cleaning something, that'll prepare you for the most efficient cleaning you can accomplish with a small/low power ultrasonic cleaner like that one appears to be. Every little bit helps!