V9 bolloxed iMovie on 4s

I upgraded my 4s phone apps, but haven't upgraded from ios7.1.2 whatever. now in iMovie video clips dropped onto the timeline are very small frames, and the larger window plays video rotated in a truncated (square) portrait mode. It's unusable. am I now forced to upgrade my iOS? Is there a benefit to it for my 4s, or will a reinstall of the app do it? Thanks.