If your jacks are not extending enough to create enough pressure, then you need put some blocks under the jacks so they will reach and be able to exert the necessary pressure. There is nothing wrong building up a base for the jacks to rest on. If you go camping and have an unlevel site, you'll need to be prepared. In the photo below, the tongue was in the gravel and the back end was in the air. Without the aid of these blocks I've carried for years and years now, we would have had a very wobbly trailer. Mine are not electric, but the principle is still the same.
FYI, as stated above, if you want to eliminate trailer shake, Strong Arms really are the best. But! The jack has to be solidly down for it to work right also. Try putting some lumber under the jacks and see if that helps. The farther the jacks have to extend, the shakier the trailer gets. Keep the jacks as "short" as possible. That's why blocks under them helps a lot.