Check the electrical connections for the control board and ignitor. Also that there is no debris in the venturi going to the burner, even a small spider web can disturb the fuel/air pattern to cause a problem. You may even have to clean the tip of the ignitor; be carful not to break the porcelin around it. Let us know how you make out.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7