I have battled this issue ever since they pushed Android version 4.2.2. On my Galaxy Tab model GT-P5113 the power + volume down would work only about once every 10-20 attempts. Since the new build was pushed last week I checked it again. Now the screen shot does not work at all.
But I gave up long ago and came up with a solution. I use my Samsung Victory telephone to take a picture of the tablet and send that to the tablet to by whatever share method is handy.
