ETA 2836 Crown issue…

[Jesterfromchester]

Hi. I need advice on what to do next with this watch. I have a ETA 2836 movement watch. I had this watch sent out to the manufacturer when it would no longer manual wind. They did a full service and sent it back. When I got it back, I set the time and put it on a winder. A couple months ago I went to set it for daylight savings time and the crown come off/out. Most of its life was spent on a winder. Now I’m very, very careful when pulling out the crown of any watch to set the date/time but the crown came out really easily. This is the only watch I’ve ever owned where this happened.  When I gently pushed it back in, it would not wind or move the hands or date at any of the three positions. It just spins with no resistance. However it still keeps time properly when I put it back on the winder. The crown rod(?) does not seem to be damaged at the tip. 

so my question is:

What is actually happening when the crown just spins? Is something stripped? Is there a term to search on or is there a good diagram that shows what’s happening internally for this specific movement?

Is this something that can normally be fixed during scheduled maintenance if I sent it in or based on my description,  is it really messed up inside? 

Thanks in advance