Well your Obviously pulling too much brake or throttle and stripping the insert's....I Only run "DNF" horns and cant say ive ever had an issue.....imo the Stock losi set-up is the best there is for buggy as it clear's the body nice and is easily adjustable...the bend linkage rod will definitely make the motor act up as im sure the arm wasn't being pushed by the spring very hard which is a common thing i see a lot.....i would replace that rod and Polish it before re-installing and it should be silky smooth....i polish my throttle side rod every so often as if its all gritty and binding in the plastic the linkage wont work very well.
Also madweazl 4mm shim's will take out a lot of the excessive slop in the losi plastics for the rods.