The error diagnostic properties provided by the "diag" object are not defined anywhere.
I/A Series (Niagara) UNC ENC
These properties are present in the controller but were not shown at the GCM level and were deemed not necessary in diagnosing issues with the controller.
Below are what the unnamed error properties represent:
error8 [err8] - Real time Clock (RTC) installed
error16 [err16] - RTC invalid
error32 [err32] - Database is being downloaded
error64 [err64] - Block frozen, will not run (not running)
error512 [ err512] - Enhanced MZII hardware
error1024 [ err1024] - not assigned
error2048 [err2048] - not assigned