The following error is shown when performing actions in Clarity.

Alert: Expired Request: An Expired request has been detected. Request has been cancelled. 
An expired request has been detected while processing a request. To recover you should use the browser back button or PPM History to return to the previous page. Refresh it and try the request again. 

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This issue occurs if a Clarity session gets lost or expired. The tokens are generated for each Clarity page and also stored in the session. If the tokens cannot be found in the session the message is displayed. 

If a load balancer is involved in the Clarity PPM setup, the load balancer configuration may need to be reviewed as it is affecting the user sessions.

Release:
Component: ODSEC

This is reported as defect DE42548. The session handling issue is resolved in 15.5.1 which is available and patch 15.4.1.4 targeted for FEB 2019.

If this is occurring in the SaaS environment, the may be able to be alleviated by having the F5 OneConnect feature enabled.This OneConnect Profile feature can increase network throughput by efficiently managing connections created between the BIG-IP system and back-end pool members. The OneConnect feature works with HTTP Keep-Alives to allow the BIG-IP system to minimize the number of server-side TCP connections by making existing connections available for reuse by other clients.

Please open a case to have the SaaS team enable this setting.