It looks right in my tests, the particles accelerate towards the OMFG with a large proportion hitting the OMFG in what looks like a perfect inelastic collision, that is they merge and the velocity and mass is added to OMFG. This creates a movement to the left of the OMFG particle.
Deleted my other comment as you replied sorry, it is 12 am and I am not explaining myself to my satisfaction.
As I said in my reply to your deleted comment, this is plain wrong. Momentum is conserved. Unlike kinetic energy (which gets transformed into heat), it is even conserved in inelastic collisions.
Take two masses A and B, place them at rest near each other. They should collide and be at rest at some point between them. However, based on the inaccuracy in the way the simulation works if one of those particles is really huge they sometimes gain a lot of energy and fly past each other.
Deleted my other comment as you replied sorry, it is 12 am and I am not explaining myself to my satisfaction.