We appear to have our launch module problems solved. A single cross connect was missing, causing massive imbalance and the crash of Mynmus III. Mynmus IV is much better, and achieved orbit as expected, the way Mynmus I was able to without problems. I think we may have the launch module problems worked out now.
Now on to attaining orbit around Minmus itself in order to deposit a lander there. Hopefully we won’t have any more issues like this!