I added some new debug statements to the apsw_attach_to_source function, and increased the busy timeout from 2000 to 4000 milliseconds.
Example of its debug log:
Code:
ATTACH DATABASE 's:/calibre/calibrelibrarycodes/metadata.db' AS 'SOURCE' ;
length of path: 42
Attaching to New Source Library: s:/calibre/calibrelibrarycodes/metadata.db
Now Attached to New Source Library: s:/calibre/calibrelibrarycodes/metadata.db
PRAGMA SOURCE.busy_timeout = 4000;
Finished: apsw_attach_to_source
Try the attached .zip by loading it from the file in Preferences > Plugins, and restarting.
Random thoughts: path length too long; OS case sensitivity; busy timeout was too short for your hardware; something that makes your flavor of Linux different from all others; using a server Linux instead of a desktop Linux?
DaltonST