I don't think anyone knows exactly why this happens. Personally I have stopped using the internal solver more than for testing while debugging the model. My experience is that the external solver is better. It also runs faster, I know what my results files are named and I can find them even after several months.
Try that with the internal solver where you either don't get any files; all files are called Adams.xxx or I have to go and change the prefix for each run.
I don't think anyone knows exactly why this happens. Personally I have stopped using the internal solver more than for testing while debugging the model. My experience is that the external solver is better. It also runs faster, I know what my results files are named and I can find them even after several months.
Try that with the internal solver where you either don't get any files; all files are called Adams.xxx or I have to go and change the prefix for each run.