Same problem. I too am on my second. And I'm ultra protective about where I store it and use it.
If you don't want to do DIY and you don't want to pay Precision to clean it, I'm afraid you don't have many other options. I know forum members have successfully cleaned their own with success. Maybe you can slip someone some cash in exchange for a cleaning?
I've sitting here patiently waiting for a GR III with that problem solved.
Here's a link to some members that have had success and shared their experiences.
Disassembling GR for sensor cleaning - PentaxForums.com
BTW, welcome to the forum