Rheem Powervent Water Heater Out every 1-3 weeks

My 16-year-old powervent water heater keeps going out (every 1-3 weeks). Whenever I notice a lack of hot water, I can head to the basement and find a small puddle next to the water heater and a drip from the drain valve - and the powervent is running.

If I power it down and then back up again, the water heater cycles through and lights. I will now have hot water within 30 minutes and for the next week or more. Is this unit ready to all-out fail, or is there a minor repair that can be done to end this cycle?