I would wonder if the top has been put down when wet and stored that way for a period of time .... time enough for the top to have shrunk. I've seen tops that have been shrunk and will not come down onto the top of the windshield to be locked, because there isn't enough material to allow the top to lay all of the way down. Before you buy the car, get it to a shop that does a lot of top replacements and get their advice as to just exactly what the problem is. A new top could set you back $2000 or more by the time its installed. Good Luck!