Diffrent base shear

[steelnz2003]

Hi
I got a silo wall building with a flat bottom slab and then 4 openings at the bottom to form 4 walls.

The building is fully symmetric in both axes.

I ran the analysis model in the 2 principle axis. I got a base shear value, then I tried to check the case if I rotated the building 45 degrees on the plan

That is to check the max shear on walls comparing both cases, but I noticed the base shear is greater.

I assume no matter the building orientation, the base shear should still be the same.

Any idea what is the issue in this case?

Thanks