One burner on our JennAir 800 gas range has difficulty igniting. Igniter seems to be working as well as the other four. Suspect that gas flow to the burner is low. When it does light, flame is lower than the other burners and will often go out when set to Low.
Sometimes you need to clean the burner with a small wire brush. they can get clogged up. Also if the cap doesn’t sit tightly on the burner head, it will cause problems. Parts 3 and 2 on the page.
Parts for Jenn-Air JGR8875QDS: Gas Controls Parts - AppliancePartsPros.com
The wrong cap on the wrong burner head would be bad too. It happens.