Nano WriteOut retries duplicate file contents when Append or Prepend is enabled

When a save fails in GNU nano, the edit buffer remains unchanged and the user can retry the WriteOut (^O) command. The goal is to guarantee that a successful retry does not duplicate the buffer's contents in the target file.

By default nano overwrites the file, but if the Append or Prepend toggle (Meta-A / Meta-P) is enabled, each retry adds the buffer again, producing duplicate content. Although enabling the backup feature (set backup) preserves a copy of the original file before writing, it does not stop the duplication that occurs on a retry when those toggles are active.

What steps should users take to avoid duplicate content when retrying a failed save? Should the Append and Prepend toggles be disabled automatically after a save failure? Is relying on backup-on-save sufficient to mitigate the risk of duplicated writes, or must users manually ensure overwrite mode is used?