2419894 - "Unable to load groups" on Fiori Launchpad: /sap/bc/ui2/start_up requests returned with HTTP 500

Error message "Unable to load groups" when logging to the Fiori launchpad.

The network trace in the browser´s developer tool (F12) shows return code "HTTP 500 Internal server error" for the "start_up" requests performed right after the "PageSets" request:

• /sap/bc/ui2/start_up?so=*&action=*&tm-compact=true&sap-language=EN&sap-client=001&shellType=FLP&depth=0&sap-cache-id=<cache id>
• /sap/bc/ui2/start_up?so=*&action=*&sap-language=EN&sap-client=001&shellType=FLP&depth=0&sap-cache-id=<cache id>

The ICM trace (dev_icm) shows the following errors when the issue is reproduced:

• *** ERROR => IcmHandleOOBData: Request for T68_U1932 cannot be redispatched [icxxthr.c    4797]
• *** ERROR => IcmReadFromPartner(id=15/193627): IcmHandleOOBData failed(rc = -1) [icxxthrio.c  2512]
• *** ERROR => IcmCreateDpRequest: Session does not exist [icxxthr.c    3432]

Fiori launchpad "unable to load groups" start_up sap-contextid redispatch , KBA , CA-UI2-INT-BE , Please use CA-FLP-ABA , BC-CST-IC , Internet Communication Manager , BC-CST-DP , Dispatcher, Task Handler , Problem