2 things:
1. There's no scroll wheel configuration for CAMtastic. TS.
1a. This goes along with there being no key-combo or mouse-action configuration for anything in Altium, at all, ever. (Only menu shortcuts can be reassigned.)
2. They never optimized the rendering, so if your board is huge, it takes forever to redraw. And, I think, that's part of what's going on here..? Try zooming an area first, so there's less to redraw.
3. If it's disappearing because it's not finishing drawing (how the /fuck/ they managed that, in the renderer, back in the day, I have no clue.. just shoddy design from the beginning), refresh the view (move it again, or hit END).
Tim