Greetings everybody, I have an alto saxophone and I have been getting a weird noise whenever I try playing the notes E 5,F 5, and D 5. Sometimes it sounds like I am not pressing the octave key, sometimes they sound great with no problems, and quite a few times when i have tried playing those notes I get like a weird fluttering sound. I am not doing anything with my tongue or trying to make it sound like that on purpose. It happened when I was playing with a Fibracell 1.5 synthetic reed, so I started using a Rico strength 2 reed and it sounded better, but that fluttering was still there. I have taken my saxophone to get looked at and repaired like 4 times. The last time was a few days ago. When I went to go pick it up I tested it out and those notes that I mentioned sounded perfect, but when I got home I started having problems. Like I said, sometimes those notes sound perfect, and other times they do not. This is quite frustrating and I do not know what i am doing wrong. Any help would be immensely appreciated.