Sudden drop in Vc when providing flared sections in Conbox

The bridge I'm analyzing has a flared girder and superstructure at the expansion piers.

This is the cross section I have defined for this bridge:

In order to directly obtain the area of steel required to resist direct shear; I removed the stirrups from the program and ran the analysis before generating the Detailed shear report.
However, for some odd reason, at the critical section for shear near the expansion pier (dv from the face of the support), there is sudden drop in Vc even though ideally, Vc should increase since the area of concrete available for shear is higher.

Could someone explain why this may be happening?

Thank you!