I have noticed that happening on a few of my posts from time to time. You may not need to dissasemble the post, I have had luck just pressing the poppet down with a screwdriver (be mindful of pressure here) to reseat the oring. I think sometimes the poppet just gets twisted over to one side...
Have you considered putting a gas post directly on your regulator? If you use a keg king or kegland reg, the ports are all 1/4 bsp, so you can attach a bulkeahd post directly to your regulator.
I have done this with mine and it works a treat.
Only downside is you will need am extra gas...