Trailer breaks lock up while breaking

Is it only the front axle and does it have Hendrickson Sure-Lok?

 

Sure-Lok is those bars that hold the rear axle suspension up when you are in a dock. If the leveling valve goes out of adjustment and doesn't allow the suspension to raise up high enough to retract the bars when you release the brakes, the front bags will remain deflated. This means there's very little tire contact pressure on the front axle and it will skid the tires every time you step on the brake pedal, no matter how lightly.

 

Is there a bar on the rear axle like the one in this picture? If so, is it retracted with the trailer brakes released?

Or is it sitting on the pad and the front air bags are deflated?

 

Could also be brakes at one or more wheel positions are adjusted tighter than others