Bob, you do not want to use silicone; it will not eliminate a propane leak. In fact, no sealants are permitted at all on propane gas flare fittings or compression fittings. Sealants are only applied to the male threads of pipe fittings, and most certainly, not silicone. If the compression ring inside the fitting is tightened too tightly, it's possible to lose the integrity of that fitting. I'm suspecting that's what happened in your instance. Or perhaps the threads on either portion of the fitting are stripped. In all cases of leaking gas fittings, it is recommended to simply replace the fitting in question. And be sure to perform (or have performed), a full coach timed pressure drop test to ensure there are no additional gas leaks in the coach. Do not use the appliance until the complete RV is deemed leak-free.