It seems that this is a known issue and has been resolved in SPS version 6.60. Please review the following release notes then upgrade to version 6.6.0.
General resolved issues in release 6.6.0
PAM-11844 Wrong value in fields caused error in dynamic report generation
Dynamic report generation could have run into an error if the query field tried to use an invalid value. It has been fixed.
https://support.oneidentity.com/technical-documents/one-identity-safeguard-for-privileged-sessions/6.6.1/release-notes/2#TOPIC-1471557