Calibre & Kobo not communicating

I have the Kobo Clara color, which is nearly 3 years old.
A few days ago while sorting books Calibre stated Error communicating with device...
calibre, version 9.8.0
ERROR: Error: Error communicating with device

database disk image is malformed

Traceback (most recent call last):
File "calibre\gui2\device.py", line 110, in run
File "calibre\gui2\device.py", line 581, in _books
File "calibre\devices\kobo\driver.py", line 2092, in books
File "C:\t\t\apsw-qgwg0sj1\src\cursor.c", line 219, in resetcursor
apsw.CorruptError: database disk image is malformed
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After trying various things I saw somewhere suggest to sign out then sign back in which will reset the database. Of course I lost all my books and the sync wouldn't restore them all (no idea how that sync button works!).

But, Calibre could then communicate with kobo and I started sending my books to the device. Had a couple of problems along the way but most were added easily.

I have been adding some more books this morning ok, but after reconnecting kobo I suddenly get the 'Error communicating with device' again.

Can anybody help fix this? I don't want to sign out, lose all books, add books only to have it happen again in a couple of days.