Class not found exception while accessing RTSM in BSM 9.26

Hi Experts,

We are recently upgraded the BSM 9.24  version to 9.26. Since then, we have been seeing "class not found exception" when trying to access the "RTSM administration" in BSM. Are you aware if this is a known issue with the 9.26 version or any suggested solution to resolve this issue ?

Thanks in advance.