With it fully extended, 1st shot sends it fwd two posistions. If I set it on the 3rd one out it does not do act as such, only in the 4th one, fully extended out.

Should I just ditch it and get a new one? Or is there something I can do with the pin to make it longer? Or the plastic may be worn?

It has about 3k rounds through it.

Who manufactured it?

Sorry, I guess that would have helped...

This one DPMS

I got it through some vendor in SGN.

sounds like the little pin that locks the stock in is not adjusted right

look at the little nut along the adjustment lever and thread it out a little so the threaded portion can lock into the holes a little further

The DPMS stock I bought had a short spring that held little to no pressure on the pin when it was in a hole. When I took it apart I found the plastic was drilled so deep it worried me it was not  thick enough to stand much use or the installation of a stiffer spring. I did find a longer spring the same size to put in it to give it a little constant pressure.  The stock is still in the top of the closet. I never used it because of this.

I also had a stock once that the pin wore the aluminum on an angle after shooting for a year or so. It would slide past the hole to the next one when you shot it. I tried running the nut off a little so it would seat deeper in the hole but then after shooting the pin bent because the small portion was to low. I had to cut the pin off to get the stock off because the lever would not retract the bent pin.