crown screws nice without movement, but not with mvt in it?

[horologist]

What have I done wrong?

 

I have a crown on the submariner case that screws onto the case nice and smooth when there is no movement in it.

 

As soon as I place the movement in it, I push in the spring to start screwing down the crown and notice that it does not screw on the same. It feels as if it only takes one turn to screw down flush with the case  When I unscrew it and do the same, it may take a couple of turns to screw down flush with the case.  I am puzzled???

 

Is it a fault with the stem being too long or is the stem cut in a way which causes this.  I don't want to strip the threads as they are so difficult to find and replace.  Any suggestions or feedback is welcomed with open arms  :clap2: