Lately I managed a constantly good embouchure. What’s extremely strange: if I play from sheet, I cramp up like crazy. Also with instructions (you know these apps and videos that literally show you what keys to press live synchronised to the track?).
When there’s no „rule“ like I jam to a backing track, or play scales or exercises like long tones or tonguing exercise, I can play for long time before jaw muscles hurt or cramp. As soon as I focus on the note sheets, I cramp up like CRAZY.
I would guess that it comes from trying to focus on two things at once: the embouchure itself and the note sheets, as jamming works fine if improvised.
Any tips? On a sidenote I can’t read notes TOO good, so that might play in it.