[D_Tomblin]

I've been banging my head with this plugin for the past 2 updates of calibre (now using 6.23). The precise error thrown from calibre is:

Spoiler:

calibre, version 6.23.0
ERROR: Cannot open file or folder as it is in use: The folder '<Path to files>' is opened in another program, so calibre cannot access it.This is usually caused by leaving Windows explorer or a similar file manager open to a folder in the calibre library. Close Windows explorer and retry.

calibre 6.23 embedded-python: True
Windows-10-10.0.19045-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.19045')
Python 3.10.1
Windows: ('10', '10.0.19045', 'SP0', 'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: Gather KFX-ZIP (from KFX Input) (2, 2, 0) && DeDRM (7, 2, 1) && Package KFX (from KFX Input) (2, 2, 0) && Annotations (1, 17, 13) && AudioBook_Duration (1, 0, 9) && Author Book Count (2, 2, 3) && Barnes & Noble (1, 5, 2) && Check Books (0, 1, 8) && Clean Comments (0, 2, 1) && Clean Metadata (0, 0, 6) && Comments Cleaner (1, 10, 0) && Consolidate All Library Metadata (2, 0, 46) && Count Pages (1, 13, 0) && Embed Comic Metadata (1, 6, 6) && EpubCheck (0, 2, 5) && EpubSplit (3, 6, 0) && Extract ISBN (1, 6, 0) && Fantastic Fiction (1, 6, 3) && Fantastic Fiction Adults (1, 3, 0) && Find Duplicates (1, 10, 8) && Generate Cover (2, 3, 2) && Goodreads (1, 7, 9) && Goodreads Sync (1, 16, 3) && Goodreads_Rating (4, 0, 0) && ISFDB3 (1, 2, 2) && KFX metadata reader (from KFX Input) (2, 2, 0) && KFX Input (2, 2, 0) && Kindle hi-res covers (0, 5, 0) && Kobo Books (1, 9, 2) && Library Codes (1, 0, 65) && Manage Series (1, 5, 1) && Modify ePub (1, 8, 1) && MultiColumnSearch (1, 0, 96) && Open With (1, 8, 1) && Overdrive Link (2, 56, 0) && Quality Check (1, 13, 4) && Quick Preferences (1, 7, 0) && Resize Cover (1, 2, 0) && Save To Format (0, 0, 6) && Search The Internet (1, 10, 1) && Smashwords Metadata (1, 0, 2) && Standard Ebooks (1, 0, 0) && TTS to MP3 (0, 6, 0) && User Category (1, 6, 0) && View Manager (1, 10, 2) && Overdrive Link Metadata Source (2, 56, 0)
Traceback (most recent call last):
File "calibre\utils\copy_files.py", line 112, in _open_file
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: '<Path to files>'

During handling of the above exception, another exception occurred:

Spoiler:

Traceback (most recent call last):
File "calibre_plugins.AudioBook_Duration.main", line 250, in update_duration
File "calibre\db\legacy.py", line 588, in set_metadata
File "calibre\db\cache.py", line 85, in call_func_with_lock
File "calibre\db\cache.py", line 1691, in set_metadata
File "calibre\db\cache.py", line 1686, in set_field
File "calibre\db\cache.py", line 1481, in set_field
File "calibre\db\backend.py", line 1726, in windows_check_if_files_in_use
File "calibre\utils\copy_files.py", line 252, in windows_check_if_files_in_use
File "calibre\utils\copy_files.py", line 136, in __enter__
File "calibre\utils\copy_files.py", line 132, in open_all_handles
File "calibre\utils\copy_files.py", line 123, in _open_file
File "calibre\utils\copy_files.py", line 112, in _open_file
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: '<Path to files>'

I'm not certain where the initial error lies, but it doesn't mention the actual MP3|M4A audiobook file, only the parent folder. Unfortunately, I'm not a python scripter, so I cannot be of much assistance.