1570 Movement Question

[swish77]

What could cause a Rolex 1570 movement, or any movement for that matter, to be super stiff to wind manually but keep time within COSC specs on the wrist? Does this mean it's time for a service despite the watch's good time-keeping? I realize there are probably a lot of variables, but what could be the primary culprit for the trouble winding the watch? It's not an issue when worn, only when it's been sitting for a while and needs to be wound manually before wearing. Any movement experts out there know about this? Thanks.

[Keeperoftime]

Yes, It's not just 1570's that do this :)

My watch maker told me on one of my watches that had similar symptoms. My Stem was worn and it was causing the issue. I'm not sure about this, as another told me it was dried oil etc.

It will be interesting to hear watchmakers/experts chime in.