I have a Bosch dual fuel slide-in range, model # HD17282U/03. ALL of the burners spark when I turn on any of the burners, but 2 of the burners sometimes do not ignite when I turn them on (even after multiple tries). What could be causing this? This has been a problem for several months--I've checked to make sure that the burners aren't wet or dirty before turning the knobs.

Do you think I need to replace the power module (based on the parts schematic, it looks like it's on the back of the unit)? Or could it possibly be loose/damaged wire(s)? Unfortunately, the screws holding down the burner bases on the 2 problem burners are rusted and stripped, so I can't unscrew them to investigate further.