Hey Ian,
I've attached the full log, and the test mission I'm using for you to take a look at, if you have time.
I've tried this both on a Steam and a fresh non-steam DCS world install. Have also tried disabling all my mods. Didn't see "witchcraft.step() failed" anywhere in the log.
Cheers,
Peonic witchcraft_test.miz dcs.log.txt