Hi,
I have the following problem and I'm not sure whether it is caused by Firefox or the Gnome magnifier.
When the Gnome magnifier is on and I scroll through text with the arrow keys in Firefox (address bar or in a web page, doesn't matter) then the following occurs:
When I reach the end of a line then the magnified area jumps to the top left corner of the desktop instead of following the caret. The only way that I have found to restore caret tracking is to move the caret back with the left arrow button.