Why does my Coil Pack crack between the # 2 and 5 cyclinders?

I have a 2002 Grand Caravan with a 3.3l v6.I keep cracking the coil pack between the # 2 and 5 cyclinders. The van will act fine for months and then without notice the coil will crack. I was told to replace the plugs and wires due to a possible grounding problem. This did not correct the problem. I have noticed that the problem came about shortly after breaking a serp belt. Also the van will starting to misfire if its put under a severe load and if pushed too hard the coil cracks. My buddy is a Master Tech at a Dodge dealership and he said to replace the ECM. I would like to avoid the cost if a simpler solution could correct the problem. The van is also throwing a code for oxygen sensor heater since this problem arose. Thank you.