Unexpected error while trying to retrieve logged-in user.

Hello SAP Mobile Experts,

we're currently in a migration project from SAP Mobile Platform on Premise (3.0) to SAP Cloud Platform Mobile Services (Neo). Unfortunately we're facing the following error in our custom Fiori Client on iOS (iPad Pro with iOS 12.3.1):

"An Unexpected Exception occurred during the back-end request: Unexpected error while trying to retrieve logged-in user."

This error can be reproduced with the following steps:

1. The app is removed from the task manager
2. The app is started
3. As the app was already on-boarded the user can login using touch ID
4. The user starts an app (we use the EPM Reference Application "Approve Purchase Orders")
5. The user sees data in the application
6. Now the user does other tasks on the iPad but the Fiori Client is still in the background
7. After 15 minutes the user returns to the Fiori Client and can continue working normally
8. The user switches again to another task
9. After another 15 minutes the user returns again to the Fiori Client. But now no new data can be loaded.
10. When the user leaves the application, the dynamic tile for the app shows an Error.
11. In the SAP CP Mobile Service logging we see the error message:
    "An Unexpected Exception occurred during the back-end request: Unexpected error while trying to retrieve logged-in user."

we've already changed the setting of the RZ10 profile parameters: http/security_session_timeout and rdisp/plugin_auto_logout according to Note https://launchpad.support.sap.com/#/notes/1914112 so that:

"Adjust parameter http/security_session_timeout and set it at least 200 seconds higher than parameter rdisp/plugin_auto_logout."

Our values are:

http/security_session_timeout = 2400
rdisp/plugin_auto_logout = 1800

So the setting is correct according to note 1914112.

Looking forward for some help.

Best regards
Gregor