Just thought I'd pass this on to at least try before you resorted to sending your camera off to be repaired.
I was having meter problems with my Pentax (6x7) sometime ago. Took it to a place in St. Louis who worked on it in front of me. I explained that the meter worked intermittently when it did work. Although, sometimes the exposure was off. They said everything checked out fine.
After much research on the net and talking to others, I tried something that I read regarding the battery. Someone suggested that rather than using a Lithium Battery in my camera, to use Alkalide or Silver Oxide instead. For some reason, it was a pain in the butt for me to find a battery where I lived that wasn't Lithium, but I did. Believe it or not...I ceased having my meter/exposure/intermittent issues all together.
Whether or not that is what you're dealing with, I don't know. Thought it wouldn't hurt to pass this on.
Regardless, I hope things work out in resolving your problems with your Pentax.