...
open the page in edit mode (the page with the ME-Include that includes an ME from another space)
open the ME-Include in edit mode
populate the "Space With Excerpt" input with the space that the ME lives in
this sets the “SpaceWithExcerpt” macro parameter
verify that the "Page With Excerpt" is just a page name, not a space key prepended with ":" to a page name
this repairs the “PageWithExcerpt” macro parameter
save the macro, publish the page
The goal of the workaround is to populate <ac:parameter ac:name="SpaceWithExcerpt"> for the macro (visible by viewing the Storage Format of the page)
Reference:
CMEP-251 MultiExcerpt Include - Server across spaces not working after copy/move