rear window

The top left curve of my rear window is coming away. (see picture below) I can see that the previous owner has put some black filler/sealant stuff on the top right of the rear, in the past to resolve a similar issue. Does anyone know what this sealant stuff is, or can anyone recommend a product...

I just bought a Z3 last week. After a test drive, the salesperson demonstrated how to retract the top. Unfortunately, much to his embarrassment, the cold temperature made the vinyl window brittle and it cracked right in front of us. (I was able to use this in my negotiation to further reduce the...