I believe the 8xxx & 2xxx codes are from ADSL connections.
On VDSL2 connections, the usual codes are:-
0 = Reboot/power disconnection - possibly actually Loss of Frame or Loss of Signal
2 = DLM initiated resync or from changing a modem setting that needs a resync to accept it.
I have rarely seen reason 1 - don't actually know what it signifies though
Very, very rarely, I have seen reason 3 & reason 4 on a couple of connections - again, I'm not sure what they signify.
I haven't seen ANY of the other codes, even when remotely monitoring a few VERY poor VDSL2 connections.