I just solved my problem with this issue. Many who had this problem say that the rumble feature was losing the battery pack connection. I noticed that when my fingers, which wrap around and touch the battery holder on the back, would touch it it would cause my controller to shut off.
So I merely took off the battery pack and you will see four gold connectors on the controller inside the battery cavity. They depress. So on the battery pack itself I just put three label stickers (very small ones or just cut something up) to build up the battery pack with some thickness. This causes the four gold connectors to depress deeper and now when the pack is jarred it doesn't lose connection.