The reason the backup file is corrupted is that to file icremarks.dbf is corrupted.
To fix this issue:
Close UBSPOS.
Go to C:\UBSPOS2015\'DATABASE FOLDER'.
Delete icremarks.dbf only.
Open UBS again, and it will generate the new file.
Issue in restoring the backup
The reason the backup file is corrupted is that to file icremarks.dbf is corrupted.
To fix this issue:
Close UBSPOS.
Go to C:\UBSPOS2015\'DATABASE FOLDER'.
Delete icremarks.dbf only.
Open UBS again, and it will generate the new file.