>>4100251It has a lever, it's a zorki 4k actually. Pic related is what happens.
I cock the shutter (pic 1), and when I fired it (pic 2), the drive rotates forward and that top cog that is supposed to push the one on the bottom (which cocks the shutter), gets over the other one. Consequence: when I push the lever, the film advances without cocking the shutter until the cogs get back into the right place, and I have to do another rotation to cock the shutter. That means basically skipping one exposition.
Also on pic 3, that is when I push the shutter button collar down to disengage the drive in order the rewind the film, you can see that the cogs are once again in the wrong place and prevent from rewinding the film as the sprocket spool is stuck. That is how I realized that something was wrong in the first place, couldn't rewind the film.
Nothing obvious seems to have caused that, I shot a whole roll and rewinded without problems right before it happened, didn't hit or drop it, was stored in a standard, clean environment.
