The scope shots in the last post were taken on the output
I probed the collector and emitter voltages and it looks like the transistor is in saturation.
The first two show the transistor emitter and collector voltages on the input side. You can see that the collector voltage (trace in yellow, with a 10x probe) goes all the way down to zero, so the transistor seems to be hard switching.
The third one shows what happens when the scope fails to start properly. The power supply oscillates at 1 MHz.
Board