Hi! And welcome to JA...let me see if I can help.
When working on a convertible top most of the time noises are caused by just the top vibrating or shaking around when driving. Also some seals will squeak when they get dry and other things like that. As a technician you can only replace parts that are broken, lubricate the ones making noise and hope for the best. The reason you are not getting a resolution is that BMW sees it as normal operation and not a failure. The weather also is a big factor with noises. It is nearly impossible to have a complete silent ride when you have something that is suppose to bend and flex as a top. The only thing you can do is wait till it get warmer and hopefully that will assist with some of the problem. If it is a rattle then I would try addressing the issue with another dealership. Explain to them the situation and that if resolved you would recommend changing dealerships to just theirs. Service managers and writers strive to get new customers especially if they can take a customer from their competition.
BMW Technician
ASE certified with over 3 years experience in BMW