I'm using ArcGIS 10.5, specifically ArcMap, and I had to apply a combination of many solutions provided here in order to be able to replace an existing service. The steps are the following: - The layers to be published as service were stored on a GDB so I created a new GDB and exported all my layers into this one. - I saved the MXD file (Save As) with a different name and loaded the exported layers through right click each layer, select properties, select the source tab, and selecting the corresponding layer exported into the new GDB. Those steps were enough to finally publish the service succesfully. Good luck and I hope my solution helps you. Best,
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