I was on a shoot with a rented EX-3 last week as I´m waiting to get my own.
When I tried to change the frame rate using the external button it didn´t work.
I suddenly got it to 38 fps, then dialed it down to 18,then nothing.
Any one else experienced this?

PS The camera was brand new

That's why I do not rent equipment.

I've had my EX3 less than a month. Therefore, I have not had that problem.

I was the first customer to rent the camera, so it was hardly from wear and tear.
Button must have been faulty from the start.