645 multiple shots problem

I have a Pentax 645 which seems to have a problem with being able to take multiple shots. It will take a picture and advance the film, but I must turn the power off and then on via the rocker switch before I can take a second picture. I have replaced both the AA batteries in the hand grip and the lithium battery in the bottom of the camera.

The problem started part way through the last roll of film and also exhibits the behavior with the blank (test) back in or with no back at all.

Anything I should check before I ship it Pentax for repair?

I had a similar problem and had to send it in.
It never made it thru the shutter cycle and like I had to turn it off/on.
I'd like to give you a quick fix, but sorry.
jack

Thanks for the reply. I guess I will be packing it up and sending it to Pentax this week.

Ian

ian,
The repair cost me about 224.00 dollars and took about 4 weeks.
jack