Camera help

[Chachi]

I have been using a film camera lately instead of digital (Fuji STX-2) and I have been having a problem and I was wondering if anyone knew what it could be.
When I get the pictures developed, maybe about a third of them have a yellowish-orange line on the left hand side of the pic, like it has been exposed..somtimes it's intense, somtimes it's barely there...

any ideas what causes this?
Thanks for any help..

Cam