Generally, when you have to PUSH a gas knob to light the burner you are bypassing a safety feature to light the stove. This safety feature is most common on ovens with a pilot light - pushing the knob disables the flame sensor to allow gas flow and flame long enough for the sensor to know a flame is present. If the flame disappears, for whatever reason, the sensor sees the cooling and closes the gas supply.
Maybe you need to adjust the sensor position on the burner in question.
Ted & Melinda
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