[JimmXinu]

I've found this one particular epub first failing in my own plugins and then realized it also failed when I tried to use the built-in Calibre viewer, Edit Book and convert, but only in the beta. Attached.

Trace:

Spoiler:

calibre 4.99.10 [64bit]  embedded-python: True is64bit: True
Windows-10-10.0.18362-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.18362')
Python 3.8.3
Windows: ('10', '10.0.18362', 'SP0', 'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: ColumnSum (2, 1, 0) && Count Pages (1, 10, 0) && EpubMerge (2, 10, 1) && EpubSplit (2, 9, 0) && FanFicFare (3, 22, 2) && Favourites Menu (1, 0, 5) && Generate Cover (1, 5, 25) && Manage Series (1, 2, 9) && Modify ePub (1, 4, 1) && Quality Check (1, 10, 1) && Reading List (1, 6, 12) && SmartEject (2, 3, 0) && SplitMergeNew (0, 2, 0) && View Manager (1, 5, 6)
Turning on automatic hidpi scaling
devicePixelRatio: 2.0
logicalDpi: 96.0 x 96.0
physicalDpi: 141.35652173913041 x 141.4020618556701
Using calibre Qt style: True
[0.00] Starting up...
[0.02] Initializing db...
[0.05] db initialized
[0.05] Constructing main UI...
EpubMerge: DEBUG: 2020-08-17 19:28:57,767: calibre_plugins.epubmerge.epubmerge_plugin(157): macmenuhack file_path:C:\Users\retief\AppData\Roaming\calibre\plugins\fanficfare_macmenuhack.txt
FFF: DEBUG: 2020-08-17 19:28:57,776: calibre_plugins.fanficfare_plugin.fff_plugin(210): Plugin FanFicFare macmenuhack file_path:C:\Users\retief\AppData\Roaming\calibre\plugins\fanficfare_macmenuhack.txt
[2.27] main UI initialized...
[2.27] Started up in 2.27 seconds with 140 books
Worker Launch took: 0.17502617835998535
Worker Launch took: 0.25510096549987793
Job: 1 Convert book 1 of 1 (𝗜𝗡𝗦𝗧𝗔𝗚𝗥𝗔𝗠 ༄ 𝙽𝙰𝙻𝚄 (Ch 1-3)) finished
Convert book 1 of 1 (𝗜𝗡𝗦𝗧𝗔𝗚𝗥𝗔𝗠 ༄ 𝙽𝙰𝙻𝚄 (Ch 1-3))
        Traceback (most recent call last):
          File "runpy.py", line 194, in _run_module_as_main
          File "runpy.py", line 87, in _run_code
          File "site.py", line 89, in <module>
          File "site.py", line 84, in main
          File "site.py", line 55, in run_entry_point
          File "site-packages\calibre\utils\ipc\worker.py", line 215, in main
          File "site-packages\calibre\gui2\convert\gui_conversion.py", line 41, in gui_convert_override
          File "site-packages\calibre\gui2\convert\gui_conversion.py", line 28, in gui_convert
          File "site-packages\calibre\ebooks\conversion\plumber.py", line 1049, in run
          File "site-packages\calibre\ebooks\conversion\plumber.py", line 993, in setup_options
          File "site-packages\calibre\ebooks\conversion\plumber.py", line 952, in read_user_metadata
          File "site-packages\calibre\ebooks\metadata\opf2.py", line 595, in __init__
          File "site-packages\calibre\ebooks\metadata\utils.py", line 46, in parse_opf
        ValueError: Not an OPF file

Unrelated: I bumped into some backward-compatibility weirdness when I ran an older Calibre(4.17 32bit) to check that attached epub really used to work.

When I tried to delete the book, I got this SQL error:

Spoiler:

calibre, version 4.17.0
ERROR: Unhandled exception: <b>SQLError</b>:SQLError: no such module: fts5

calibre 4.17  embedded-python: True is64bit: False
Windows-10-10.0.18362-SP0 Windows ('32bit', 'WindowsPE')
32bit process running on 64bit windows
('Windows', '10', '10.0.18362')
Python 2.7.16+
Windows: ('10', '10.0.18362', 'SP0', u'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: EpubMerge (2, 10, 1) && Generate Cover (1, 5, 25) && Modify ePub (1, 4, 1) && Favourites Menu (1, 0, 5) && SmartEject (2, 3, 0) && Count Pages (1, 10, 0) && Quality Check (1, 10, 1) && SplitMergeNew (0, 2, 0) && FanFicFare (3, 22, 2) && EpubSplit (2, 9, 0) && Reading List (1, 6, 12) && View Manager (1, 5, 6) && ColumnSum (2, 1, 0) && Manage Series (1, 2, 9)
Traceback (most recent call last):
  File "site-packages\calibre\gui2\actions\delete.py", line 405, in delete_books
  File "site-packages\calibre\gui2\actions\delete.py", line 379, in do_library_delete
  File "site-packages\calibre\gui2\library\models.py", line 416, in delete_books_by_id
  File "site-packages\calibre\db\cache.py", line 62, in call_func_with_lock
  File "site-packages\calibre\db\cache.py", line 1655, in remove_books
  File "site-packages\calibre\db\backend.py", line 1676, in remove_books
  File "site-packages\calibre\db\backend.py", line 886, in executemany
  File "c:\t\t\apsw-cjr7a2yu\src\cursor.c", line 1136, in APSWCursor_executemany.sqlite3_prepare
  File "c:\t\t\apsw-cjr7a2yu\src\statementcache.c", line 386, in sqlite3_prepare
SQLError: SQLError: no such module: fts5

Apparently 4.99 changes the library DB in a non-compatible way?

(I realize I'm back a beta version, but my wifi and power are still down. Running on generator and cell data.)