Some of the plugs and lights in trailor are not working but do have some power goin to them?

Even though some are not working other plugs on same breaker work fine. I checked connections that is how we know there is at least some power to them. What could be wrong?

Remove the cover plates and check the voltage at the connection where it comes into the box the outlet or switch is mounted in. If there is voltage there, you need to replace that switch/outlet. If there is no voltage, you have an open connection between there and the breaker, most likely located in a junction box.