- Unoconv converter is enabled (may be any other converter).
- Students submit various files to their assignments.
- Unovonv fails to convert files and leaves records in the mdl_file_conversion table with status = '-1'.
- Admins configure and enable new file converter (may be LibreLambda or any other plugin).
- New file coverter successfully converts all new files, but all failed pre-existing conversion remain unconverted.
- Even if students re-submit same files they still fail to get converted.
- Students can tweak and re-save their files (which changes file contenthash) so these new files get successfully converted (as there is no record with failed status in the mdl_file_conversion table).
- When a document converter is enabled/disabled all failed conversion should be deleted from the mdl_file_conversion table.