In case anyone finds this in the future (not 100% sure if this would have resolved the original issue, but this was the only thread in Geonet that matched the same error…):
I was encountering the same "Exporting data changes failed" error in Field Maps following making some minor changes to the feature layer schema (added some fields and updated some domain values).
After some head scratching, I deleted the newly created fields and slowly added them back. What seemed to trigger the issue was a long field name (which was 42 characters). Once I re-created the field with a shorter name (31 characters), all issues with creating and syncing offline maps were resolved. Unfortunately the error messages were not very helpful in diagnosing this issue… But perhaps it will help someone else in the future.