Firstly, do a visual inspection on all the fittings and tubing. There should be a flexible hose coming from the master cylinder, that connects to hard tubing and will Tee and go to each of the brakes. Check everything over from the master cylinder to each caliper and look for wet spots on the trailer frame and calipers. Also look for busted hoses and tubing.
If you don't find the obvious culprit, just go through with a wrench and tighten all the compression fittings, they should be nice and snug, but not overtight. Also check the bleeder valves on the calipers. You may also want to check your calipers and pads. Jack up each braking wheel where the suspension bolts on, never in the middle of the axle and remove the wheel.
With the wheel off you can get at the caliper bolt on the back, it should be one bolt, but may be two if you have the upgraded brakes. They are self adjusting and float on that bolt. Check the pads for wear and make sure the caliper pistons have not come out and the boots are in decent shape. If all is well put them back and put a bit of lock tite on the main bolt and tighten it down.
On the actuator itself, you may also have a bad shock, this shock helps balance the master cylinder and softens those hard blows. You may simply want to refill the cylinder, bleed the brakes, and try hand pumping it and looking to see if the brakes are still leaking.
I suggest replacing any and all parts that look shadey. I recently replaced the entire braking system on my 2002 trailer, they simply wear out. I did it myself for about 700, everything except the lines, but i needed rotors too. I dealt with DHM to get my parts and they are top notch and their website is the best, good pics so I could match the parts. You can trash the actuator if the shock and the master cylinder is shot. It's a pretty easy replacement though, One hose and some retaining rings.
UFP's website has PDF guides on the calipers and actuator as well as bleeding instructions and install instructions. Good luck and post how it all turns out.
Oh crap, I just noticed it's Grant. Hope this helps!!
http://www.dhmtrailers.com/online/home.php http://www.ufpnet.com/