Created attachment 119372 [details]
When I saved that file, all the x-refs were fully assigned.
This bug is rather difficult to circumscribe. The best description I can provide is that the systems loses cross-references (which then are represented as "Error: Reference source not found" fields) when we open documents that already contain them.
Thanks for reporting this problem!
It is already known in another bug. I set this one as duplicate.
*** This bug has been marked as a duplicate of bug 94804 ***