As 1ns max step help, and I expect you don’t want 1ns max step other than switching moment, this is what to consider in Qspice.
Add a buffer in front of switch. You can define a TTOL for buffer if you need more timestep at switching moment. (In default, ¥-Device with TTOL=1us)
Default model Diode 1N4007 still not simulate in this setup, but model likes MURS160 can work. By far this is something I can think of.
I have a post about a study of TTOL device to interface analog and digital in Qspice. I am not sure why, but with a ¥-Device in front of a Switch normally work better with a Switch defines with a TTOL parameter.
TTOL device to Interface analog and digital - QSPICE - Qorvo Tech Forum