Paperless-ng docker on Synology DiskStation -> Consume folder mounted from Linux via NFS

[amenk]

I have the following setup. Paperless-ng is on a Synology DiskStation where I created a shared folder for the document consumption.
I mounted this folder on a Linux laptop and I am scanning via a bash script.

After scanning to a temporary folder, the script does a

"mv $TEMP_DIR/output.pdf $OUTPUT_NAME"

Where $OUTPUT_NAME is on the NFS folder.

Consumption by paperless-ng it basically works, but it seems to try to consume the same file lots of times:

[2021-12-18 16:12:06,433] [INFO] [paperless.consumer] Document 2019-02-01 20211218_170846 consumption finished

[2021-12-18 16:12:07,169] [ERROR] [paperless.consumer] The following error occured while consuming 20211218_170846.pdf: UNIQUE constraint failed: documents_document.checksum

Traceback (most recent call last):

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 84, in _execute

    return self.cursor.execute(sql, params)

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/sqlite3/base.py", line 423, in execute

    return Database.Cursor.execute(self, query, params)

sqlite3.IntegrityError: UNIQUE constraint failed: documents_document.checksum

The above exception was the direct cause of the following exception:

Traceback (most recent call last):

  File "/usr/src/paperless/src/documents/consumer.py", line 287, in try_consume_file

    document = self._store(

  File "/usr/src/paperless/src/documents/consumer.py", line 382, in _store

    document = Document.objects.create(

  File "/usr/local/lib/python3.9/site-packages/django/db/models/manager.py", line 85, in manager_method

    return getattr(self.get_queryset(), name)(*args, **kwargs)

  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 453, in create

    obj.save(force_insert=True, using=self.db)

  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 726, in save

    self.save_base(using=using, force_insert=force_insert,

  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 763, in save_base

    updated = self._save_table(

  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 868, in _save_table

    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)

  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 906, in _do_insert

    return manager._insert(

  File "/usr/local/lib/python3.9/site-packages/django/db/models/manager.py", line 85, in manager_method

    return getattr(self.get_queryset(), name)(*args, **kwargs)

  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 1270, in _insert

    return query.get_compiler(using=using).execute_sql(returning_fields)

  File "/usr/local/lib/python3.9/site-packages/django/db/models/sql/compiler.py", line 1416, in execute_sql

    cursor.execute(sql, params)

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 66, in execute

    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers

    return executor(sql, params, many, context)

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 84, in _execute

    return self.cursor.execute(sql, params)

  File "/usr/local/lib/python3.9/site-packages/django/db/utils.py", line 90, in __exit__

    raise dj_exc_value.with_traceback(traceback) from exc_value

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 84, in _execute

    return self.cursor.execute(sql, params)

  File "/usr/local/lib/python3.9/site-packages/django/db/backends/sqlite3/base.py", line 423, in execute

    return Database.Cursor.execute(self, query, params)

django.db.utils.IntegrityError: UNIQUE constraint failed: documents_document.checksum

[2021-12-18 16:12:07,492] [DEBUG] [paperless.parsing.tesseract] Deleting directory /tmp/paperless/paperless-bz81_8u1

[2021-12-18 16:12:07,647] [ERROR] [paperless.consumer] Cannot consume /usr/src/paperless/src/../consume/20211218_170846.pdf: File not found.

[2021-12-18 16:12:07,975] [ERROR] [paperless.consumer] Cannot consume /usr/src/paperless/src/../consume/20211218_170846.pdf: File not found.

[2021-12-18 16:12:08,484] [ERROR] [paperless.consumer] Cannot consume /usr/src/paperless/src/../consume/20211218_170846.pdf: File not found.

[2021-12-18 16:12:08,993] [ERROR] [paperless.consumer] Cannot consume /usr/src/paperless/src/../consume/20211218_170846.pdf: File not found.

[2021-12-18 16:12:09,501] [ERROR] [paperless.consumer] Cannot consume /usr/src/paperless/src/../consume/20211218_170846.pdf: File not found.

[2021-12-18 16:12:10,004] [ERROR] [paperless.consumer] Cannot consume /usr/src/paperless/src/../consume/20211218_170846.pdf: File not found.

The file is deleted properly by the consume job from the share.

What could be the reason for this to happen? Did anybody else see this behaviour?