What you encountered is trap ringing with using trapezoidal integration. Search the keyword “trap ringing” in forum to get more information, there are multiple discussion threads as your reference. Here is one of my summary,
Voltage oscillation in different transformer modeling approach - QSPICE - Qorvo Tech Forum
LTspice and Qspice are quite different in certain area, and trap ringing is one of it. Mike explained why he no longer smooth trap ringing in Qspice in this reply
Need guidance on qspice integration method and this feather parameter - QSPICE - Qorvo Tech Forum
Initially, people may think prior art is better, but it just hide a problem that you should be aware of. In your case, few things can help
- .option maxstep=10n - reduce timestep
- .option feather=.1 - trap with feather (experimental damping)
- .option method=gear - change of integration method (to gear integration)
maxstep is the best amount them.
Trap ringing in general appear in simulation with near ideal component in SPICE.
Or, if you change Vh=+0.1 to Vh=-0.1, your simulation file can also run reasonably. It force the switch to smoothly transition between on and off.