Whirlpool Gas range -intermittent brolier(only)

I have an interesting problem with the broiler. I’ll turn it ON (broil –> start) and then wait and see the flames ignite, then come back in 5 minutes, expecting the broiler pan to be heated and ready for meat - and find that the broiler is OFF and the oven barely warm. Pressing the "start" button again gets me the three "I’m already ON!" beeps … so I have to turn it off (Cancel) and then Broil –> Start again.

An important note here - the OVEN is not intermittent. The oven works correctly every time AND is within 5 degrees of accurate.

Since the oven works every time, I’m guessing the temperature probe isn’t the issue - so this leaves, as far as I can see - two possible culprits (A) The Gas Valve or (B) the Control Panel/Control unit.

So I ask

  1. How to test?
  2. Any other possibilities?
  3. Any suggestions?