That motor and ESC combo is asking a lot of that lipo. Running mod is the only time you really have to have a higher C rated battery. that battery might not be getting hot but I bet the wires especialy at the solder joints are. I had the same issue when I was running two 2s packs in series in my 1/8th. was running good 35c lipos but the solder joints on the bullet connectors to the batteries kept coming unsolderd. I switched to 50c packs and never had the problem again.