What was your first RV noob disaster (or near disaster)?

First camping trip in our first motorhome. Our daughter was with us and said she could hear a sound like dripping water. I said it was just the water heater relief valve dripping outside, like I knew what I was talking about. We awoke to a lake in the living room from a leaking water filter under the kitchen sink. Ever since, we turn off the water at night and when we're away.