No, that is not normal. The piston seals off the ink chamber; behind it, that is on the piston knob side, no liquid belongs. If water collects there after flushing, either the piston seal is no longer tight, or the pen was held too deep in the water for too long, so that moisture worked its way past the seal. Standing moisture in the barrel attacks the mechanism in the long run and should therefore not simply be accepted.
A stiff piston points in the same direction: the seal has dried out or hardened and no longer slides. Forcing the knob round at that point risks breaking the piston mechanism, which is far more involved to repair than renewing the seal. Both cases belong in expert hands, that is with the factory service or a workshop specialising in writing instruments, where the seal is replaced and the mechanism regreased. On a Meisterstück only a few years old, a leaking piston is normally a matter for the guarantee or for goodwill. Until the repair, leave the pen open to dry out completely and do not fill it again.