Symptoms
When logged it to branded localized MyCP as a service user, one can observe that APS application specific tabs may switch their translation between languages while navigating the CP and switching the tabs.
In /var/log/pa/pui/pui.log on the UI node, the following messages can be found, note the locale value:
08:30:37.507 [default task-140] DEBUG c.p.p.c.c.a.util.APS2CustomUIHelper - Calling NavApi: refresh: false, request:Navigation: {depth=10, placeholder=http://www.aps-standard.org/ui/user, locale=pt_BR}
08:30:54.951 [default task-176] DEBUG c.p.p.c.c.a.util.APS2CustomUIHelper - Calling NavApi: refresh: false, request:Navigation: {depth=10, placeholder=http://www.aps-standard.org/ui/user, locale=en_US}
08:32:14.829 [default task-33] DEBUG c.p.p.c.c.a.util.APS2CustomUIHelper - Calling NavApi: refresh: false, request:Navigation: {depth=10, placeholder=http://www.aps-standard.org/ui/user, locale=es_ES}
Cause
The issue is acknowledged as APS-40669 (Navigation menu item translation changes on switching CCPv2 tabs).
Resolution
Contact TAM/PTA to clarify the status of the request and request a hotfix.