Newbie Trailer Brakes question

I'm a total newb when it comes to my boat trailers.
My trailer is a EZ-Loader that came with a '99 Cobra, the ones with the square tongue and fill port for brake fluid with a breakaway cable.

Recently, I noticed that when I slow down on the road the trailer makes a rattling sound right before I come to a stop.
I'm guessing it's a brake issue, but have no idea what I need to do.
In the past, I'd always take it to a shop, but with these tight times I decided to try working on it myself to save some cash.

Anyone have any guesses to what may be the problem?
And how often should I be greasing the hubs?

Sounds like the DB42 brake system. You may only be experiencing partial braking on the single bolt caliper system. Try unplugging your trailer from the tow vehicle and backing up a hill. If the brakes come on, leave it in reverse and check to see at what point the front pin is on the side of your actuator. If the pin is 1/2 to 3/4 of the travel in the slot, the brakes are bled properly. I'll bet it goes back all the way and you may not have brakes at all. The noise is most likely coming from the pads rattling on the rotors from lack of pressure. Upgrading the brake system is fairly inexpensive and easy. Most likely you will have bearing lube hubs or Trailer Buddy's on your axle. Bearing lube has a rubber plug in the center of the cap that covers the bearings. Greasing is recommended each time you launch. Trailer Buddys have the blue piston with the zerk fitting on them usually behind a stainless steel cap. If the protector does not show any blue between the cap and the body, pop the cap off with a pocket knife and add grease. You should see the blue piston as you do your walkaround before towing. You will find a lot of useful information in downloadable pdf files at ufpnet.com if you wish. Click on Actuators and watch the videos that explain the concept of the braking system. The disc brake tab will have the information on the brakes, and the Axle tab will have the various booklets to match up with the hubs.

I was a total newb about boat trailers until I had to service practically everything on mine in the past 2 months of owning my boat.

If you unplug the trailer harness and attempt to back up do the brakes lock up?

Do you have a surge brake setup? If you do maybe it has something to do with your actuator.

I'm in Portland too so if you need a second pair of eyes let me know.