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