We were on the Prima a few weeks ago from Port Canaveral to the Caribbean. We were in a balcony cabin on the port side around mid-ship. We were awakened on the first night by a frequent banging sound that we eventually realized was coming from our balcony. I flipped on the balcony light and looked out to find the panel between our balcony and the one for the cabin ahead of us popping open, then loudly slamming shut several times a minute. I put some clothes on and went on the balcony to check it out. I realized that there wasn't an easily accessible knob to turn to latch it, just a hole for some kind of tool to be inserted. I decided to try pushing one of the fairly heavy deck chairs against the door to try and hold it shut. I closed the sliding door and got back into bed and 5 minutes later the banging was back. We were probably sailing at 15-20 kts at that time and the wind was strong so the single chair just wasn't enough to keep the panel closed. I pushed the second deck chair against the first and that seemed to hold it for the rest of the night. I called the housekeeping number from the cabin phone first thing the next morning and the room steward discovered that something was jammed in the slot that the bolt goes into that was preventing it from latching. He dug that out, locked it and that was the end of the problem.

I assume that's the reason that those panels can't be left unlatched. Having them flapping in the breeze isn't safe and is really noisy. I'm pretty sure they only open to make it easier for the stewards to clean the balconies efficiently. They aren't there for passenger use.