this type of error is unfortunately not very useful in debugging a model. It basically means that the solver couldn't handle the simscape portion of your model. This could be due to something in the model being unrealistic, or it could be issues with how the solver is set up. It would be helfpul if you shared you model. The most common cause of this is an unrealistic simulaiton. Examples would be accidentally leaving out free wheeling diodes on an inverter, or accidentally shorting some terminals or leaving something open circuit that shouldn't be. On the solver side, you should always start with ode23t for electrical simulations. The first thing you can do is tighten the tolerance to 1e-4 (not sure it will help with this though). Switching to a local solver with fixed step can often bypass issues like this but if you don't figure out what is wrong you will never be able to go back to variable step which is more accurate and should to be used to validate a fixed step size. Since it specifically happens at 0.4, there might be a switch or some change to the network happening specifically at that time which is causing the simscape network to be unsolvable. This might give you some hints as to what part of the model is causing the issue.