This error most commonly happens when your solver cannot handle large fluctuations in signals. Try using ODE15s (Stiff/NDF) as your solver.
Go to model configuration parameters(Ctrl+E) > Solver and adjust
Solver: ode15s (stiff/NDF)
This should fix the issue.
Read the Documentation for ODE15s here:
If not, you can also try:
- Adding a delay so that the fluctuation slows down.
- To find out more, try adding Port Value Display to your signal and then step through the model.
Hope it helps.