[Northwind]

Hello together,

since a few weeks I get an error when trying to open books with the build in reader after changing metadata (book title)

The files are not corrupt and open fine after importing them into calibre.

Whenever I change the title (ususally I modify the title of a book in a series to include series name and number), the book won't open. After changing back to the original title, erverything is fine.
calibre version is 0.9.18.
I think, this happens since 0.9.16 or sowhere around, not sure.
It happens with both mobi and epub formats.

Error is
caliber unpack requires a string argument of length 2

Traceback (most recent call last):
File "site-packages\calibre\gui2\viewer\main.py", line 40, in run
File "threading.py", line 504, in run
File "site-packages\calibre\ebooks\oeb\iterator\book.py", line 99, in __enter__
File "site-packages\calibre\customize\conversion.py", line 239, in __call__
File "site-packages\calibre\ebooks\conversion\plugins\mobi_in put.py", line 32, in convert
File "site-packages\calibre\ebooks\mobi\reader\mobi6.py", line 79, in __init__
error: unpack requires a string argument of length 2


Any Ideas ?