ok race day my losi kept cutting out?

i landed on my lid and pushed the heat sink on my mm in a bit, after that i put the medusa in there, come race day it would totally lose everything, steering, throttle everything. for one second, then it would go again, today i ran a whole pack through and it didnt do it once? but i did change the pack,. but how could the pack do that? im bewildered right now!