UWL completed items refresh for system: SYSTEM error: ENQUEUE_EUWLNOTIFREG:already locked error

Dear all,

after an upgrade from EP 7.01 to 7.31 SP8 we checked our NWA logs and found following exception to be thrown periodically:

UWL completed items refresh for system: SYSTEM error: ENQUEUE_EUWLNOTIFREG:already locked error.

Location: com.sap.netweaver.bc.uwl.core.push.NotificationThread

Our backend system is an ERP 6 EHP 6.

We have unfortunately no idea, why this error occurs our how to handle it. Im not able to find any informations on this issue on SDN or SAP Marketplace. Could anybody help us on this please? Thank you very much,

regards