Most of us who are here answering questions are fellow users doing this in our spare time. With all due respect, that time does not include watching lengthy videos when a brief explanation will suffice.
I watched your video long enough to ascertain that you had a rehearsal mark which appeared to have moved off screen/page and were trying to move it lower – hence my reply, which gave you a procedure for doing so (switch to Engrave mode). For that matter, @Janus’s reply made the same point, about the difference between Write and Engrave.
If you think you’ve found a bug, please describe it clearly and provide the shortest possible example for others to reproduce it. I can’t tell exactly what you think is a bug – that the rehearsal mark is positioned too high? There are a number of things that could legitimately cause that, but we can’t tell exactly what’s going on unless you post your project here.
We do welcome reports of bugs, because we’d all like to see such things fixed. Please help us understand whether what you’re seeing is actually a bug.