Don't assume that purchasing a new trailer will automatically result in reliable brakes.
My experience with different types of boat on different trailers, but which is with over-run operated brakes with wire [as opposed to rod] operated brakes, is that they are extremely sensitive to adjustment.
I suspect that rod operated over-run brakes are slightly less sensitive to that adjustment.
However, whichever you have, the principle of over-run brakes is inherently crude, and if you set them up to give good response, you will always be on the verge of having binding brakes = overheating = bearing failure. If on the other hand you set them up to avoid risk of binding, the towing vehicle brakes will always do the majority of the work, and you can expect to be smacked up your tail end every time that you have to brake hard.
Even what I have to say above assumes that you have not only ensured that your linkages are all free, but that you have also ensured that the bowden cables connecting the wire or rod linkage to each wheel are equally free. In reality, they are very often the cause of poor brake response in an otherwise apparently well serviced and adjusted system. Disconnect them, and check that the internal cable is moving freely within the outer. If not, some have grease nipples in their mid-section. My local farmer, who owns five trailer boats ranging up to 50ft! swears by immersing the bowden cables in diesel to free them off.
Lastly, I endorse Geoff Harwood's recommendation of RM Trailers - the owner, Richard Gifford-Hall, has extensive experience of making and altering trailers for a variety of Seal/Parker models. They converted a Seal26/Parker 27 trailer for me so that it could be simply switched between carrying a 26/27 and a 22 as required.
Geoff Sheddick
Geoff Sheddick
Parker 27/146 "Stroller'