I have overhauled / rebuilt Matco Brake Master Cylinders for two different RVs. Both have worked find for the past 2 years or maybe I should say I have not had any complaints come back that they were leaking again.
I have Clevelands for the past 24 years on my airplane. (Rubber replaced numerous times. I like 5-years or 1,000 flight hours whatever occurs first.)
Typically on my own airplane, the new RUBBER parts or kit fix the leaks. IF there is scuffing on the steel or aluminum parts, then they may leak again soon. I like to take a Scotchbrite pad over the areas of steel that has wear marks so that it is smooth. IF it is smooth to the touch, I do not get leaks any time soon.
The Matco kit for overhaul / rebuilt is around $15 or was the last time I checked. There is one seal that is sorta like an o-ring on the inside of a washer. That part I have been unable to find without buying the kit. It is one of the parts that does need replaced.
I would try to rebuild / overhaul using the Matco kit. IF you have leaks any time soon after, then the replacement master cylinder may be needed.