I recently started playing again after 16 years. I would up shifting to cornet due to the group i am playing with is a British Brass Band. Now that I have been playing a while and started playing various horns, I notice some seem to center better than others. I have a run that I am practicing that goes from Bb, C, D, C Bb, C, D ,C, Bb, C, D, C, Bb, A, Ab. all sixteenth notes middle staff. I find that on most of the horns I have played it flows very easy and is responsive. and I can kinda just blow though it and it sounds good. Now I pulled out my Bach strad, and play the same run, and behold I it seems to not center the D and I experience a flub note that really doesn't hit. I experienced this also on a older 60's Holton Super Collegiate, just didn't want to hit certain first valve notes well. The principle in my Brass band tried the horn and told me something in the valve(s) just is off or a design issue or just a bad horn. If my memory serves me, I had a similar issue with my 91 Bach Strad. I am not sure if something like this is a mouthpiece issue gong from cornet to trumpet. I am using a V cup versus bowl cup. So the question is, is this a horn issue, or a problem between player and horn from cornet to trumpet issue, and I just need to play it more?