Having already done adjustments and replaced multiple parts, you've really ruled out potential mechanical causes here. A next step would be to look at the electrical side of things.
Specifically I would look at connection points in the wiring on the trailer to make sure all of the connections are correct and redo them. A short in the wiring to the back axle brakes could be the cause. During your thorough inspection of the wiring, look for any pinched, frayed, or damaged wires would... view full answer...
Since you have installed Item # LC379146 and you are getting current, I recommend checking the voltage. If you are getting current but not enough voltage the steps will not work. A few other things to look at and test. Check the grounds to make sure they are good, check the door switch to make sure you are getting voltage to it. Another way you can test the steps is disconnect the two wires and connect the red wire directly to a battery. The steps should extend out. To get them back in... view full answer...
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