This is a known issue with VSF Omegas, mostly on SMPs, more rarely on other models.
In fact, it's such a common problem on VSF SMPs, that it's pretty much expected to happen sooner or later on yours if you own one.
The problem is caused by excessive wear on the crown tube's screw-in thread. There's a quick and dirty solution by cutting down the tip of the stem until the distance between crown and case is as if it's screwed in. Of course this is not really good for the water resistance.
The correct solution is to replace the crown tube. In case of the SMP, it's easier to get parts since the VSF SMP uses standard Asian-ETA 2824-2 parts as opposed to the VSF clone movements which use a rather erratic mix of different Asian-ETA parts (A7750, A2836, A2824 etc.) + VSF custom parts.
If this problem arises on one of the VSF clone watches (there recently was someone on RWI with a Planet Ocean A8500 VSF having the same issue with the crown tube thread), it's harder to get replacement parts as VSF doesn't supply any at the moment.