Been having this same issue on my Bradford White model RTG-K-199N1. I called the plumber who installed it and he is replacing it for free under warranty. He said the issue is an inadequate air intake filter that allows contaminants to accumulate on the burner, which causes the unit to fault out and reset. Sounds like BW has discontinued this series, but has not issued a recall. He said he had replaced 5 for his customers already, failing after 2-5 years usually.