Stuck shutter

[Alakh]

I bought a used Nikon 50mm f2 -AI & a FM 10 from two different vendors.When clicked the shutter remains half activated,When I release the lens ,it completes full shutter release .i don’t have an extra lens to verify error and it fires clean when clicked without attaching lens.
Pls advice

 

[dxqcanada]

Does the shutter open/close on it's own when the Speed Dial is set to B ?

 

[Alakh]

It remains open as long the shutter button is pressed and closes when released

 

[Alakh]

oops sorry, would reply yes