Re-install Display Glass On Back Case?

[Usil]

I just finished timing my IWC power reserve and was successful in getting it to about + 2 seconds a day. I had just finished and had greased the o-ring ready to put it all back nice and tight when the display glass fell out of the back.

It is possible that I pushed on it and made this happen during my handling of it but in the off chance it actually is loose, it kind of defeats me sealing up the watch water tight without addressing this issue.

What can I do to insure it stays in place and water tight? I am looking for a relatively easy solutions here as I want to do it myself? Besides press fitting it back in place, is ther something else that some people do and have good luck with when this happens?

Usil