Hello All! I am a french horn player firstly but have been playing the trumpet as a hobby for about 10 years. A friend in my orchestra recently gave me a like-new Giardinelli 512 which was an upgrade from the barking dog I was playing on before. This trumpet had been sitting in a storage unit for a while and had apparently not been played in a long while. My problem now is that the first and second vales are sticking something fierce. I have oiled them and the mechanisms look good so I cannot figure out why this is happening. I can play for about a minute without them getting stuck and then all of a sudden the first valve gets depressed and won't come back up. Like I said, I'm normally a french horn player and I've never had formal lessons on the trumpet so I don't know that much about them other than how to play. Any tips on why this might be happening are appreciated. Also, the valves are in the proper position, clicked in place.Thank you for your help!