Just encountered this on a different question. The related Calc or Writer documents connect to a database via the registered DB name. If the 'package' is moved/copied to a different system these related files are trying to access the DB to refresh via the registered name. If that specific name is not registered to the correct DB you get the error.
Simple enough to fix. On the relocated system, simply register the DB with the same name as was originally used.
Edit 9/24/2017:
To insure not screwing up anywhere, just performed another test as laid out in both questions.
- Used portable split DB (as you have) in Dropbox folder.
- Created Calc file linked to this .odb in Dropbox folder & placed in split folder. All works OK.
- Copied split folder to new location.
- In new location, opened .odb & deleted a record.
- Opened Calc in new location & refreshed data. Still shows record I supposedly deleted.
- With the Calc file still opened, changed Registered name location to point to new location of .odb.
- Again, using still opened Calc file, refreshed data. Deleted record was now not in list.
It is all in where the registered name is pointing to.