I have a 2016 VW Golf that I can't quite turn on. This morning, I stuck my key in the ignition, and the lights on the dash popped up like normal. As soon as I turned the key, everything went off, I heard a "pop" from under the hood, and the engine didn't start. I tried taking my key out and re-inserting, but none of the dash lights came on and the engine didn't start. Thought it was a battery issue so I jumpstarted the car and went to a shop to check. No issue with the battery apparently, but there was a buildup of minerals around one of the battery connections (which the tech thought was causing the issue). He took the battery out and reinstalled it, and my car started up like normal. I drove 30 minutes home, and turned the car off. I tried turning the car back on to double check, and the same problem happened again where I heard a pop, and the lights went out. I can't lock my car using the fob from either inside or outside, and I've changed the battery on my keys. What is causing this?