This definitely did the trick for me, thanks @Npsm! Focussing now works a lot better than before! Just for those of us, who need some help with disassembling the camera module…
First remove the camera module as described in:
(you can change the language settings in the top menu)
As soon as you have removed the camera module, you will see one more tiny screw that needs to be removed to disassemble the camera module:
Also remove the latches (2 on one side and one more on the other side):
Then you should be able to easily remove the back cover of the camera module (perhaps you might want to use a tiny screwdriver as a lever). The open camera module should look like this (the actual camera within the red circle):
You will actually need a screwdriver now to carefully remove the camera from its mount as it is firmly attached to the mount by sticky foam (the foam that is actually causing the focus problems). Once removed from the mount, you can realign the sticky foam so that it does no longer disturb the movement of the lens of the camera. It should look like this in the end:
Reassemble all the parts carefully and enjoy your new FP2 camera feeling:
(taken on my FP2 with the realigned sticky foam)
Thanks to @Npsm for this great solution!