As per what I found online and Scott Blum mentioning the same...
Has to do with the 8 speed not having overrun clutches in them and if you stop or slightly go backwards, while in drive, the trans will stall out the engine. He also mentioned he can easily recreate it with his 3.6.
The fix forward?
Adjusting driving style, not fully lifting off the gas, just barely keep some pressure on there to keep it from stalling. So for me, left foot braking even when lockers are on only while doing the more interesting obstacles. My habit is that once lockers are on, I usually don't left foot brake much. Not a big difference in technique as I am already used to LFB.