Roof leak, help!

Last summer on our last trip we got an inch of water in the back of the refrigerator below the gas and power connections. It was coming down beside the fridge through the insulation there. I sponged it up every half hour while it was raining. At home I didn't see anything obvious at first but after taking off the vent cap I could see the caulking around the base was cracked. Upon removing the calling I could see there should be a double sided sticky pad between the vent and the roof but nothing but air there! It was already fall so I just caulked it again. I was thinking of putting eternabond in that gap but then realized that might make it impossible to take the cap off later. Would appreciate some advice on that.