I've had this issue since I bought the scenery one and a half years ago but I just never bothered to do anything about it since I've spend many hours trying to fix it myself but at some point just got too frustrated and completely gave up.
Now with v5 and a massive performance improve I'd like to fly into EDDK a bit more often but my elevation seems to be messed up at EDDK still:
I think this might have something to do with ORBX GES. Now that this scenery is out for quite a while I figured there's likely a fix for this since I can't imagine I'm the only one with that issue.
Addons I'm running that might interfer with AS EDDK: ORBX Global, ORBX Vector, ORBX OpenLC EU, ORBX GES
I'm running P3D v5 with basically a clean install, the above mentioned ORBX products and some other airport sceneries.