Rehearsal Marks not staying where I put them.

I am trying to put rehearsal marks - A. B. C. - on a piece of music. I cannot get them to stay where I put them. They want to go either to the top or bottom of the score or a random measure. I included a zip file of a video of what if happening. Oddly, Musescore doesn't allow unzipped videos. Is there something I am doing wrong, or is this a glitch.
thanks