I found some AXL Error Codes, 5000 - 5007 (5006 missing), but there have to be more.
For example I also received a -239.
Is there a documentation on the AXL Error Codes? Perhaps there is a database table containing the AXL Error Codes.
Like the database tables from Cisco Unified Communications Manager 12.5(1) Database Dictionary:
https://developer.cisco.com/docs/axl/#!12-5-cucm-data-dictionary
There are tables like
typeadminerror
typedberrors
containing error codes and messages, but none for the AXL Error Codes (like mention above, 5000 - 5007, -239).
Where are those AXL Error Codes defined, and the messages?
The AXL error codes are not documented and may change per release (though very unlikely to see anything but additions), but may be useful when working with Cisco Developer Support.
Examining the AXL service logs on CUCM may provide some clues for the errors as you encounter them.