Simulink 2019b Fnc block not working

I'm using a Fnc block in Simulink in a motor modeling simulation and it is not working. I'm using the Fnc block to model torque ripple by setting the block to sin(6*u(1)), where the input u(1) is the motor rotor angle theta and the Fnc output should be a sine at 6x the rotor frequency.

If I use sin(u(1)) I do get an expected result, but if I use sin(6*u(1) the result is wrong. I have a relay block after the Fnc and it works in all cases.

sin(6*u(1)) sin(u(1))

It's almost like the Fnc block does not sample every simulation step. It is a continuous time simulation.