Skyler_kelly69 is right to be careful, but saying heat will "soften the locking mechanism permanently" is a bit off. Modern vinyl plank locking systems are made of PVC or a similar polymer. You aren't melting it, you're just making it a bit more flexible for a moment so it can slide. It's like warming up a plastic zip tie to bend it, it goes back to its normal shape after. The real risk is holding the heat in one spot too long, which can cause a local warp. A quick pass on low heat is usually fine.