Its funny cause LAS Vegas had this problem awhile back and evetually was updated.
KLAS hasn't been updated, at all, to fix this problem it never had to begin with.
The only change we did, that had anything to do with the elevation issue, is that our Live Update previously didn't recognize the presence of the OrbX fix so, if you installed the OrbX fix and then ran the FSDT Live Update, it would remove the OrbX fix. Now, the Live Update recognize the OrbX fix and doesn't remove it anymore.
But as I've said, if Michael_B767_ATP reported the solution worked for him at KDFW, if he using FSX and you are using P3D, it might explain why it doesn't work as well for you, if the OrbX AEC utility still hasn't been updated to recognize sceneries installed in the P3D way.
Of course, the problem doesn't have anything to do with KDFW, and there's nothing we can do from our side, to change the behavior of that utility. Last time I enquired OrbX about the KLAS elevation issue, which was too caused by their products, I got no answer.
Fortunately, no all OrbX developers are the same. Last week, I got an email from an OrbX developer who did the right thing (checking if HIS soon to be released product MIGHT cause a conflict to an already established FSDT product that has been on the market for years), and of course he got full support from me, with a free copy of the scenery to test his product with.