Just done mine here.
Similar to Holeshots pics, leaves/soil (decomposed leaves?) in the wiper motor area and as good as a blocked drain.
Grease on the copper plate was a bit less, but cleaned it all right up.
Now working.
Forgot to plug the damn wiper motor in afterwards though haha, so had to re-remove a few bits to get a few fingers in and slide the plug on! 5 mins second time round!
I think I have two scuttle clips left now. I had a windscreen fitted in July, and six had black silicone repairs on them, all of which broke upon removal again. The scuttle clips slide into a clasp on the actual scuttle, and it is those clasps which break away it seems, leaving the damage on the scuttle panel with no other way to repair

I reckon doing this in winter is a bad thing too, the plastic is very brittle even at 10degC. I'd go as far as saying lifting the scuttle 5mm and blowing a hair dryer in on hot would be a good idea as the plastic will soften up lots, probably making it a great deal easier to remove without damage...
Looks like a new scuttle is about £85, tempted to get one, along with all new clips/screws. Much like anything I bet ALL these bits were fine until they were touched by a person who had little care for it (Autoglass person), and they damaged it all.
http://bmwfans.info/parts/catalog/E85/Roadster/Europe/Z4_3.0i-M54/RHD/N/2004/june/browse/vehicle_trim/various_body_parts/#01
One thing I don't get though, is the scuttle clips. Are they meant to leave the white part in the bodywork, and leave the small black shaft with the blob on the end on the scuttle, or is the white clip meant to come out too?
In any case, I'd massively recommend using lots of white grease inside the white bit, so they stay put and the black shaft with the bobble are the bits that slide out in future... it feels like it's meant to do that!
Just a few more jobs to get the car in perfect order for spring time
Dave