Hi @mrgt ,
Don’t know the answer or whether this is a help or not but since you really have nothing to lose …..
Here’s a link to a video that shows how to dis-assemble an Intuos 4 pen.
I realize that it is not the same model as yours but perhaps it is similar enough in design that opening your model may be the same.
If you do get it open and have any further questions, post back here (with images of the problem if you think that it would help) and hopefully get more detailed help.
Here’s how to do this Voeg afbeeldingen toe aan een bestaande vraag