Mine runs away with me, did so three times over 1 1/2 mile stretches at the weekend. I have owned him 14 years, hes 19, I have come to the conclusion that he will never change. He does it through excitement and enthusiasm. Its not a bolt just a damn wont stop whilst its fun.
Fortunately he has a brain and stops if going dodgy, gate in the way, pedestrians or traffic!
I would not try to wind him up further by running him in company. The one time I tried this he went for 39 mins none stop before I pulled him up and i could never ride on the same stretch fo ground again. Mine has ER race ride background so he doesnt get slow as a concept!
I find the best thing with mine to maintain control is to go with the flow and actually push him into the bridle and retain steering , if i fight him I lose as hes stronger. Schooling makes no difference as he does a good controlled dressage test - hs just runs of in a balanced manner now! Sorry not helping your problems (if it is one), just trying to say it just happens with some horses so there you go!