Thomann EP 904 GP Bb-Euphonium

the instrument is good, everything is assembled very high quality, the instrument sounds great in the lower register, I would say that it is too good, but the problem is different, in the upper register, starting from E and ending with A, all the notes are too high, but especially this F, it sounds like a full-fledged Gb and is almost impossible to play on it, I tried to pull out the first crown almost completely and, lo and behold, the note sounded, but the rest of the notes already have to be lifted with the lips, which is very difficult and inconvenient