Which STAAD version are your using? Can you attach that model for the investigation?
Existing PR VERIF_24JAN.STD STAAD.Pro CONNECT Edition - Version 22.07.00.160
I was not able to reproduce this issue in the latest STAAD.Pro CE version 22.12.00.142. Please try to upgrade to this STAAD.Pro version and check if this resolves the issue.