Cursor Jumping has me jumping up and down in rage

This may not be a Scrivener problem but perhaps a Scrivener user has experienced and fixed it. When I’m typing and often after a pause and I start typing again, the cursor leaves the word mid-way and jumps above (or below if there is text) to a different position/line. It’s SO frustrating. On my old iMac, I decreased the font size and that helped mitigate the problem, though not entirely.
On my new MacBook Pro I can’t really decrease the font size and still work comfortably. I checked the cursor size in Preferences but it is set at Normal, which is as far as I can shrink it. This problem occurs in MS Word too but not as much, I think. I even changed the Apple wireless keyboard on a suggestion of one friend, but that has not helped.
I should add that I use a Japanese language keyboard (I’m resident in Japan) though use it mostly to write in English. Could this be the problem?

Note that the font size and the Zoom setting are independent. You can set the font to Flyspeck 4 and zoom up to 600% if you like. I don’t know if that will fix the problem, but it’s an available parameter space to explore.