Concerning faults: I inspected two T-samples. One without any marks of use on the plunger only released erratically. That may be due to the plunger mechanism, or the shutter itself. The other sample with matted plunger stem, works continuously but is a bit stiff and needs relubrication.
Still in the shop it worked stiff as above. But at home after only a dozen or so cocking actions a threshold was to feel that got harder with each cocking, the same time I realized that the frame counter works only erratically. The threshold resistance after few further cockings got so strong that I fear for braking something... The camera is now queing for the workshop to get the plunger mechanics looked after.