The Fixed-step size is the time interval after which the solver solves a Simulink model. Hence, all the sample times in a Simulink model must be an integer multiple of the fixed-step size. In your example, the fixed-step size is 10000000(e7). And the sample time for the block 'Drivetrain/Drivetrain/Discrete-Time Integrator' is '5e-5', which is not an integer multiple of e7.
To solve this issue, you can set the fixed-step size of the model to be 'auto'. You can find this settings in the Solver > Solver Details > Fixed-Step Size in the Model settings.
Hope this helps