New 330ci convertible owner with small problems

[Suffolk330ci]

Evening, just bought my first ever BMW 330ci convertible on a 2002 52 plate, has been well looked after and had a lot of money spent on it but have a problem with the passenger rear window? It seems to go up all the way but when I shut the drivers door there's a slight gap and not lining up properly, is there a cog in the motor worn so it lifts up but drops slightly when fully up? Other than that there's nothing else wrong with it and I love that straight 6 three litre lump,

any ideas or problem solving would be most appreciated,

thanks John