I'm with Yankee2500 on the weakened recoil spring = pounding the pup's innards. Changing the spring every 200 rounds or so is cheap insurance. At today's ammo prices, the spring costs around the equivalent of 3 rounds of premium carry stuff. My early R9s has 2,000+ rounds. I'm down to firing a couple of mags per month, and hope to continue doing it that way until the pup's an old dog.
Years ago I bought a H&K USP in .40S&W. H&K was very reluctant to sell me a replacement recoil spring assy. (It is a double spring set-up similar to the Rohrbaugh.) The H&K factory rep told me to send the gun in if I ever felt the recoil spring was getting weak. I talked him into selling me a new recoil spring assembly with captive large spring. After three or four thousand rounds I could feel the slide hammering the frame as it cycled. Changed over to the new captive spring assembly. After another three thousand rounds, I could feel that slide hammering the frame again, but by that time, Wolff was making recoil springs for the USP. I switched back to the original loose-spring recoil assy., added the new Wolff recoil spring, and haven't had to change it again. Wolff makes good springs. I understand they are making springs for Rohrbaugh.
Lesson here is you have to listen to what the gun is telling you.
Incidentally, I bought a Ruger LC9 a few months ago, for those times when I don't want to put my R9s in messy situations. It works well, but it is 6" long, a big difference compared to the 5.2" Rohrbaugh. The LC9 has been 100% reliable from round one. Have about 500 rounds thru it. Called Ruger to get a couple spare springs, etc., and the service rep said there is no recommended interval for recoil spring change, but it should be well over 1,000 rounds. "If the gun begins to fail-to-extract or fails-to-feed, then the springs should be changed." I thought, "Great, wait until a concealed-carry gun screws up before performing maintenance. Here we go again!" He didn't give me any trouble about buying spare parts, though. The LC9 has a (cheap) plastic recoil rod and two loose concentric recoil springs, but they seem to do the job, as spring length has changed minimally since new. That extra 0.8 inch overall length difference compared to the R9 really is functionally significant. I recall speaking to Karl Rohrbaugh one day and he said they really tried to keep the R9 overall length under five inches, but just couldn't get a recoil spring to work properly. So, the 5.2" length was grudgingly arrived at.
Sorry for the long stream-of-consciousness message, but one gun thought lead to another and.....