I'm working in a project with whole Europe data. I'm working with WGS84 (4326), and sometimes I overlay my polygons with Google maps layer (in QGIS) to see some details. When I do this, I have to reproject all the data to EPSG:3857, and it shows without problems.
In the image, Portugal coast matches with the polygons.
The problem comes when working with switzerland data. I'm seeing that not overlays 100%, but it shows a difference of +-500 meters.
In the second image, coast of a lake in Switzerland, is 500 meters moved. Does someone knows why could could be happening this?
The rest of countries don't show any problem too. The only problem I see is In switzerland.