i experience that exact same thing. i can be in the middle of a block and completely loose all of my breath without even making a sound. tho i havent really thought about it that way, i just assumed it was the side effect of having a stutter that is basically all blocks. honestly you might be right thought, i’ve never been good with breath stamina in general. what i’ve come to learn myself is that despite being a “speech” impediment, it doesn’t seem (at least to me) exclusive to just speaking. i play guitar, have been for many years, and i have these exact same speech blocks when playing sometimes. although it seems to mostly only happen when i’m trying to learn a new song, or reading a tab.