A slight wobble of the turning section and a somewhat stiff extension are known on many 146s and 149s, more pronounced on one example, less on another — not a defect, but generally disliked. Stiffness often arises from dried ink residues; these can be loosened by an ultrasonic bath or by rinsing. Water or ink behind the piston does not belong there: it is mostly the result of solid ink deposits that produce a gap between piston and barrel. With modern writing instruments with a plastic mechanism, this is mostly uncritical; with older writing instruments with brass mechanism, this can rust. Hot water or DIY attempts should be avoided with celluloid models; in case of doubt, repair by professionals or with special tools (e.g. from penboard.de) is advisable.