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Replacement parts for WHIRLPOOL KGRC608LSS0 30" Freestanding Gas Range Designer Style Convect | AppliancePartsPros.com

Does this mean that the keypad has to be replaced?
Yes, that would be my first item.
Unfortunately the pin-out for the keypad is not available so it is difficult to check with a meter.
Often keypads will have a number of keys that us a common line/wire on one side of the switch, it sounds like that line is open/dirty/broken.

I would try the following first

Connector Cleaning / Checking
Unplug the unit
Open it up
Remove the ribbon cable from the keypad to the control board at the control board.
Clean the edge connector.
If it is the type where there is not a connector just the insulation is removed, it can be cleaned with a pencil eraser. Do not use an ink eraser as it is too abrasive.
Check the tracks in the ribbon cable for hairline cracks. A magnifying glass helps here.
Would not hurt to clean the connector on the board. Use electronics contact cleaner or isopropyl alcohol and a tooth brush. Be gentle and do not reconnect till all the solvent evaporates.
Reconnect everything and give it a try.