Strange staff space in one page only

I’m in Engrave and on my drum part page 3, and only page 3, has a large space at the top of the music frame. There are no flags visible so no explanation. Help!?

No idea, but I observe rehearsal mark F has disappeared. Related?

What does it look like in Galley View?

Also, what does it look like in the Vertical Spacing sub-mode of Engrave Mode?
It is possible to move the last system on a page (only 1 staff in this case) out of sight below the bottom of the page by using the square edit handle on the left-hand end of the system. Similarly for the first system on the next page ie moving it above the top of the page, thus creating a very large space underneath. If this is what has happened (only a guess on my part), then it might explain where rehearsal mark F has got to.

Interesting case for me because when I tried to move one fermata to be on the barline, it took out like 4 or five bars, when on page view in full score view.
When I changed the fermata option back to original setting, all bars came back.
Very weird.

Well thanks Andro. I didn’t notice that letter F had disappeared, and only in THAT part! So just for grins I poked around the menus at the top of my screen and stumbled on Engrave > Staff Spacing > Reset Layout… and suddenly Letter F appeared! in the empty space no less! Still a mystery though.

You had perhaps (inadvertently) dragged it off screen when you were last in that layout?