Can anyone identify what part is necessary to be replaced? It is a gasket on the convertible top.

I had this same issue, just use some glue and stick the rubber back down where it belongs, you will see where it goes. open the roof a bit until the roof starts to fold and push the rubber back down into the crevice where it sits, you should be able to easily tell, and apply a little glue to keep it there.

Depending on how much you use the top all sorts of "stuff" comes out, but not had that happen.