my 180mm sliver shutter bug
The shutter on the silver Mamiya C330 180mm lens is cocked by an 'extender' arm that links the face board cam to the shutter, which is located a distance out along the lens assembly. My lens extender arm is lightly worn, so that unless you give the shutter cocking lever an extra nudge, afte rthe extender arm has operated as a part of the film advance, the shuter sounds like it is working properly, but the blades do not open.
I have not sourced a fix. I just have a flouro post it taped to the top of this lens that reminds me with the words 'Shutter Cocked?'