Garmin chart offset issues

[PatrickG]

I'm using a Garmin 3006C, with Med charts, in southwest Turkey. Sailed to the small island of Kastellorizo, just a few miles off of the Turkish coast, and the chartplotter was more than 300m off from our actual position. I have searched for information about Garmin chart errors for this region, but found nothing - which is a bit disconcerting. As it was daylight it was pretty clear we weren't where the plotter was saying we were. Any suggestions? All help much appreciated!