What makes a Cisco device generate logs like this?

[hurtlocker87]

%AAAA-3-INVALIDLIST: % AAA: invalid authentication list 1.

I can see logs for a user login successfully then this logs is generated which is followed by a traceback number.

according to https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/16_xe/smg/xe-16-10/b-sem-16-10-1/b-sem-16-10-x_chapter_00.html

%AAAA-3-INVALIDLIST : %% AAA: invalid [chars] list [dec].

Explanation

One of the AAA methods lists has inconsistent settings

but what does this means? if the user is already logged in?

[MHM Cisco World]

Share config 

MHM

[Joseph W. Doherty]

BTW, generally, tracebacks are bug related.