This is because Staad reports the SF as per the local axis of the member . When the member orientation changes, the SF changes accordingly .
Let me name the nodes as 1 2 3 4 (from start to end) .
As per the loading, the SF at node 3 (end of segment 2 and start of segment 3 beam) should be -93.15 KN .
If all the beams have the same orientation,. Staad reports the correct diagram ( following the left up right down shear convention) .
When the orientation of the last beam is changed, the start and end point changes, keeping the left up right down SF sign convention, Staad plots this SF diagram .
use PRINT MEMBER FORCES and check for the SF result and you will notice the difference . Also, check the individual SF diagram using the member query to understand the left up-right down sign convention.