Thanks for making an appeal, here's what I found last night from reviewing my recorded demo:
I'd like to preface this first clip by saying that the MP5's recoil doesn't need to be compensated for in such a severe manner like you'll see in the video, and I'll follow up with another clip of a different player who also uses the MP5 against zombies for comparison.
And the comparison with another player, as promised:
Baseline Zombie Comparison_2.mp4
The same erratic behavior can be found in these other two clips, shown at 50% speed for clari