Yep, the lens shutter is open no matter what I do...
I double checked the self timer but it doesn't affect anything
The only case where I can remount the lens on the body is if I push the shutter release button on the body, the mirror goes up and the red pins match (red pins on the lens under the bottom of the arrow / holes on the body at 11 o'clock) but it's clearly the wrong position because then, when I advance the shutter knob, the mirror won't go back in down position. It blocks somewhere halfway and the viewfinder is dark. I have to remove the lens to finish the advancement and fire the camera.
I think my lens is jammed because I didn't shoot for a very long time and Kowa lenses don't like inactivity... :(
If my lens is jammed though, I still don't understand how I could finish a film roll just before this happened...