You have to take the shrink wrap off. OR, use meter leads with a sharpened tip to poke thru the wrap. I have had a battery pack open up between cells (broke the weld bond). It was about 3 years old in a trainer I used for skydivers and dropping toilet paper (funflys). There was no bad vibration and the battery was insulated in foam. It just happens. I am also hearing about this more often now from others at the club and here. Since I've gotten into giant warbirds I spend time checking the packs visually at the weld points and cycle them a few times when new just to be sure.
Edwin