Problem with(adding) tempo markings

Chromebook/linux i5 mouse imput 4.5

Just saw 4.5.2 update this morning. Sorry if it was addressed there. Did not think I saw it, though.

Working an orch score. 10 instruments, 12 staves.

All was fine till near the end 200+ meas. Was adding a tempo change. (allarg, though rall did same)

Added to top staff, then was copying to a couple of the other staves. As I did so musescore added the markings to the first 7 staves. If I tried to cut any of them they all disappeared.

I then looked back to a couple of other meas with tempo changes. They also, now, had the markings on the first 5 instruments, only. (2 were the grand staff instruments) Went back to first page and the same thing at the beginning.

Some of the changes had all the markings visible, some only the first instrument was visible, the others grayed out. Obviously, something I had not done. I could not cut any markings without all on that page disappearing, but I could at least gray out individual markings. There were also numerical tempo bpm added, again some visible most grayed out. In all cases none of the last five staves of the score had any markings.

None of this is too critical, but very annoying and problematic. I mentioned this because it is an issue that should not occur.

I have started the next movement and none of this happens early on. The first time I noticed was after 200 meas. I will watch as the work progresses. Is there any way of knowing how many notes in a score? I also wonder if that has anything to do with this.