Hello,
Generally, the XYZABC values of the physical and virtual tool always have to be the same. If they are not, you will have differences between the simulation and the actual robot.
So if you change the simulation to B = -90, you have to do the same with the robot!
Note that KUKA|prc uses X as the tool axis (which is not a setting of the robot, it only affects how the ABC values have to be laid out).
Does that solve the problem, or does it still occur?
Best,
Johannes