My TF Corsair is over 10 years old and the gear have never had an issue since new. I use silicone oil both light and heavy and the gear operate smoothly and at lower pressures. I add light oil to the air lines each season or so and that keeps things lubed for a while.
As for air I use as much capacity as I can put in the airframe. Usually that’s a large tank and medium tank or like in the YA P-38 it has two large tanks for gear and one medium tank for brakes. You cannot go wrong with more volume, it only improves performance and reliability in these retract systems. I also use air line restrictions for both up and down circuits so they don’t slam up and down to lock.
As far as the locking arm goes I have seen them misaligned but the main thing is that the air cylinder can move freely to actuate the locking arm. I suggest before someone removes the arm they make sure the cylinder does what it’s supposed to do and the arm is able to lock and unlock as designed. None of my Robart gear, Corsair, P-51, Hellcat, etc, have ever had a locking problem in the last 15 years. The most recent Hellcat gear are the first to be poor from the factory and I fixed them so maybe these count as the first bad set I guess.
Side note: I still have a full set of electric actuators and controller for the large Robart gear new in bag. I’m never going to use them so if you need a set let me know.