STRYKIE
Are ya' ready for MK11 kids?!
So apparently this happens by setting the training dummy to record/playback mode and setting to reset in the same position, after a couple of attempts at trying to punish Sub-Zero's B2 and resetting accordingly, I noticed I wasn't in the left corner anymore, so I kept going, and low and behold, I ended up out of bounds into some weird void, couldn't move, and Scorpion's hellfire particle effects started going apeshit.
I can only vouch that this happens for sure on the dead woods stage, I tried a couple of others and it didn't happen, although I don't know what the situation is on every stage.