hmm that happens to me some times also, what i do is when using speed hack, i stop every couple of seconds just to let the game catch up with your speed hack, cuz i noticed that when u run with speed hack, and have a different computer running and a player in your party, your green dot doesnt move untill you stop then it catches up.. and also ive noticed that when i go outside of the map, into the black ground to kill in python, they disapear alot more then if i attack in the map first then walk out into the blackness, idk try what i said, hope i helped, GL
Edit- also try staying away from other people, legit and vacers both. sometimes they can mess up your mob