If a record is failing to sync between Re-Leased and Xero and can't be resolved by updating it in either system, there is an option to "Unlink" the record and exclude it from future syncing.
How to Unlink/Link
1. Select the flag and find the line with the error. Click on the validation message
2. Take note or copy the 'Id'
3. Open the Sync Results page, ensure the filter is set to 'Linked' or 'Show all' and enter the 'Id' into the search bar and you will see your linked record
4. Select the record, the select 'Unlink Records'. This will now be ignore in future syncs
Unlinked records can still be shown under the filter 'Unlinked'. If you want the unlinked record to sync again, you can relink it but if you haven't fixed the issue, it's likely the sync will fail.