Intermittent spark ignition systems for restaurant cooking equipment?

I am working on a Blodgett convection oven (propane) which is equipped with a Johnson Controls G770 type spark controller. My problem is that after the pilot flame is detected and the main burner solenoid valve is energized the main burner lights for about a second and then both the pilot flame and the main burner flame are extinguished. The ignition system then recycles with the same result, ultimately going into lockout. Replacing the control yields the same result so I have discounted the possibility of it being at fault. Any suggestions? The factory offers no viable solutions.