Blown head gasket

I replaced the head gasket about two years ago. About two weeks ago the same van had symptoms of a blown head gasket. And I confirmed it by seeing bubbles in radiator fluid and also water and oil mixture by looking in the oil cap and white smoke coming from tail pipe. What is puzzling is this van has not overheated since I fixed it. The temperature gauge has remained very steady throughout. What I did notice though was the top radiator hose was contracting back and forth. I checked on thermostat and I assume it had remained locked. It was defective. Could this cause a head gasket problem. I also heard this vans are known for blowing head gaskets. Is this true?Because of design problems. Please give me expert opinion.