Raymarine E90 chartplotter help

[Barra]

Hi

Got a dilemma with an older e series chartplotter.

I had a licenced raymarine repairer look at my chartplotter in Athens Greece last year because it was unable to read the navionics CF card beyond 12 mile range (the unit just froze when you zoomed out) This took over 1 year to start happening.

The problem apparently was that the CF card was 2gb and the unit went into paralysis trying to read it. Chart was replaced by the technician with a 500mb version with all the same mediterranean charts that is labelled "only for sale with raymarine" and the zooming problem stopped. He also did a software update.

Now I have a new and much more dangerous problem -

The chart offset varies widely from one location to another ie on one island its 1000 feet east out, in another maybe 30 miles away its 700 feet north and 300 feet west etc. Other places its spot on.

The actual GPS coords from the unit are accurate checked against 3 mobile phones GPS.

Because the boat and the unit are currently half a world away (and there is no offset problem at the current hardstand location) Im trying to work out if the problem is the new chart or the unit maybe due to software upgrade?

Thanks