I have tested removing the stem in all positions on two different VS3135 movements. If done carefully, you can do it in any position, but I had the best luck not fucking up the keyless works in the
time setting position. Here is what I did (note: first timers need to use less force on everything than they assume)
Winding stem removal:
- Pull stem to time setting position and set time to ~6 (make sure date gear not engaged just to be safe)
- Start pulling the stem outward with just a tiny bit of force and press the release button with even less force until it releases
- Pull out very slowly, with a slight clockwise twisting motion if needed
Winding stem insertion:
(This is where you are most likely to fuck it up)
- Insert the stem slowly and as straight in as possible while turning it clockwise
- If you've properly engaged the sliding pinion, you should feel almost no resistance until its almost all the way in
- Then it should click in to time setting position
If you've managed to mess up the keyless works, this position makes it easier to fix from the back. (You only need to remove four screws to get to the keyless works FYI). It's pretty easy to fix, here is an example of what is usually wrong (sliding pinion gets pushed out of place):
Here is what it should look like: