Error caused due to nstep



I am testing out the full body models with some motions that i extracted from sensors.
I am able to use the sensor readings as input to models and get a proper output.
But, I need to get the same amount of output anybody readings as the input sensor readings.
For instance: if i have 50 sensor readings, then i need to get 50 muscle power output.
For this reasons, when i had 68 sensor readings, i changed the nstep = 68. But, it is throwing the following errors.
Muscle recruitment solver : solver aborted after maximum number of iterations
If i change the nstep to either 67 or 69, then i get a proper and accurate output. But, i need only 68 outputs. I have also tried changing the following.
But, it still gives the error.
Please let me know how to get over this issue.