Ok, call me ignorant or whatever, but I took out one Parker Reflex with cracked and heavily stained cap and took out the nib just to find out how to do it. After I put it back, it worked and felt quite like before, but the nib and feed can now be turned and taken out quite easily. Is that somehow normal, e.g. caused by the cheap construction of the pen or will the nib "sit" in its place after some time using it? Or have I probably damaged something?

Hi,

The nib of a Reflex should fit with enough friction that it does not fall out or turn while you are writing. It should not move around unless you purposely move it.
Reflex pens have a plastic that does not seem to age gracefully, so I wouldn't be very surprised if something had split (the plastic does not really crack, it quietly splits instead)

Dillon

Well, while writing it feels exactly the same as before, only when I displace it again, it comes out quite easily, that's the difference.