Hookedup1

I have an issue with both my HDS8 and HDS5 Lowrance units in so far as Lake charts not being in the correct location. I had both units upgraded to latest software version at the NTC/MWC in Escanaba MI. by Cap't Ron. (What a great guy) anyway my charts with contours seem to be 200 feet off from actual location --mostly in E-W direction. Has nayone run into this problem? would I be better off with an exteranl antenae?
Had Lowrance 525DF and it always seemed to be right on. I don't know what is going on with these untis -- I am beginning to suspect the update version. The HDS8 & 5 were showing i should be in 35' of water at Bay De Noc and my depth finder read 8ft of water. Same thing is happening on South Long Lake in Mn. --I need to be able to rely on my charts with some kind of accuracy.
Anyone have any ideas?