Kobo Communication Error when sending Metadata

Calibre v3.48 (64 bit)
OS Win 7 Home Premium SP1
Kobo Aura 2 (most recent firmware)

Kobo connects to and communicates with Calibre fine, I can send books to Kobo from Calibre fine, but keep getting "Error Communicating with Device" message when sending Metadata (immediately after sending books)

Error Details:
calibre, version 3.48.0
ERROR: Error: Error communicating with device

IOError: disk I/O error

Traceback (most recent call last):
File "site-packages\calibre\gui2\device.py", line 90, in run
File "site-packages\calibre\gui2\device.py", line 543, in _sync_booklists
File "site-packages\calibre\devices\kobo\driver.py", line 970, in sync_booklists
File "site-packages\calibre\devices\kobo\driver.py", line 2519, in update_device_database_collections
File "site-packages\calibre\devices\kobo\driver.py", line 3198, in set_core_metadata
File "c:\t\t\apsw-mc0now\apsw-3.27.2-r1\src\cursor.c", line 236, in resetcursor
IOError: IOError: disk I/O error

Things I've tried so far:

-reboot computer and Kobo
-delete metadata.calibre and driveinfo.calibre from Kobo
-factory reset and fresh setup of Kobo

After the factory reset and fresh setup, I was able to load books and metadata for about 50 books, but then when adding two more I got the same error message again.

Kobo displays Title and Author fine, first 50 books show Series information, but subsequent books do not show Series info.

Is this a limit with Kobo that it can only store Metadata for limited # of books? I have stored >600 books on the device, but for some reason can't store Series info for all of them.

Any suggestions or assistance most welcome!