Opening a file with an Xref, or Xrefs, after saving may appear to be moving/relocating on their own. Explore INSBASE and UCS commands as the most often fix that works:
Both the value of INSBASE variable and the current UCS need to be consistent in both the source and target file(s). The easiest way to keep all of this straight is to set UCS command settings to World and INSBASE variable setting to 0,0,0.
Use 0,0,0 as the insertion point when you INSERT the Xref. The same if you are creating an external block with WBLOCK command.