I've been noticing some intonation issues on my Bach Omega..
When I play a low D to a G it sounds fine.. When I go up to the D from the G it's flat enough pour syrup on it and eat it as a pancake! As I'm becoming a bit stronger up there and utillising it more it's become more and more apparent..
I don't remember having a problem as a kid (playing the same horn after a few years away).