In early March I upgraded to Desktop 10.4, but since then have republished a few map services running on ArcGIS Server, which remains at 10.3.1. In recent weeks I have observed several service crashes and am now suspicious my Desktop 10.4 to Server 10.3.1 publishing environment might be a contributing factor. Can someone advise me on this? I'm trying to rule things out, and would be grateful for any help.
It should be okay to publish from a higher version Desktop to a lower version Server. This article says that you can publish from a lower version Desktop to a higher version Server .Compatibility of ArcGIS 10.4 for Server with earlier versions—Documentation | ArcGIS for Server . If you still have problems, you can try to save your MXD to a lower version and then publish. File > Save a Copy.