All Plugins are the latest versions:
Clearcase plugin version 1.6.3
Jenkins LTS 2.49.1

Changelog used to change login names to Real Names as stored in Jenkins People.

This no longer works - login name is displayed.

This is a big step backwards.
Login names of x123sbr05 are useless in a list of changes - it used to be converted to Joe Bloggs
This is a recent regression.

None of the plugins above ( clearcase scm ) have changed recently, can't pinpoint which one yet.

Plugins updated on 14 September
ldap
git
workflow-durable-task-step
warnings
analysis-model-api