Yeah, the slide just falls off if you remove the eyecup. I might give it a try with something small to stick in there, but is there anything else inside there I could damage?
---------- Post added 30-12-14 at 11:04 ----------
Tried editing, but since my account is still too young I will have to make this a seperate post... :P.
I took a chance and stuck a knifepoint in there. The viewfinder is back in focus now
. I might send it in when I get back home, the camera is still within warranty for another 2-3 months. So hopefully that covers this issue as well. Otherwise I will just leave it as I don't need to adjust it anymore.