another place to seal to prevent leaks

We were camping during the heavy East Coast rains in Sept. and found another leak. The inside front wall in our bedroom slide was wet. I got up there and found an opening at the very top right at the outside corner. Looks like it has never been sealed. I guess the real heavy rain made the leak show, we never noticed this before. I looked at the other slide corners and they didn't look that great either. I am going to seal them tomorrow. Might want to check the slide corners. I believe this could leak for a long time and not show if the rain wasn't heavy. We do have toppers over the slides but with a heavy rain they didn't help too much.