[mitch13]

I have a very large library (in the tens of thousands). All has been going well for a number of years and Calibre performance on this large file is excellent.
While working on my library recently (wanting to transfer all pdf files to a separate library) my PC had a problem and when it had finally recovered from its 'fit' had lost my entire calibre library.
I did have a total backup even though it was a couple of days old and so I copied this library folder to the folder that had held my current library (now non-existent). Calibre then opened with close to the number of books I had.
On running a library check it pronounced the library healthy but when followed by the next stage check I had a large number of books physically in the library but not in the database.
After awhile and getting very nervous I decided to run a Restore Database believing that this would solve the problem. I have tried many times now and always during the second of three stages my PC goes into my least favourite mode ie 'Not Responding'. I then have to kill Calibre via Task Manager.
Debug message:

calibre Debug log
calibre 2.19 [64bit] isfrozen: True is64bit: True
Windows-8-6.2.9200 Windows ('64bit', 'WindowsPE')
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Starting up...
Problem creating accessible interface for: CalibreSplashScreen(0x332b3f0)
Make sure to deploy Qt with accessibility plugins.
Problem creating accessible interface for: QScrollBar(0x87f5d80)
Make sure to deploy Qt with accessibility plugins.
Started up in 12.60 seconds with 0 books
QTextCursor::setPosition: Position '1' out of range
QTextCursor::setPosition: Position '382' out of range
QTextCursor::setPosition: Position '87' out of range


Any suggestions to recover my library built over about 4 years!

Regards

mitch13