Key Needs to be Pressed Repeatedly to Start Working
If there is a software issue - you could replicate it with an external keyboard.

It's likely a failure in the wiring or mechanics of the keyboard. Depending on how close the Apple Store is, you might have them check for lint or debris under the key cap.

You could DIY - but the pieces are very, very fragile and you might be out some $$ to order a replacement if you break things checking it out.

At the store, they usually have spares on hand and can order the right parts on their dime if they break it during cleaning / servicing.