Switzerland is changing its coordinate system to CH1903+ or also called Landesvermessung 95 (LV95). Yes, it took some time from 1995 to now but today, a lot of data is transformed.
To use CH1903+ datasets in WebGIS environments together with Esri Basemaps the data needs to be transformed on the fly by ArcGIS Server. These Transformation must be configured in the map document, otherwise there will be a shift in your data when using it as FeatureService.
Settings on the dataframe: