A common problem with them is that when people remove the tubes they get aggressive and crack the tube at the O-ring groove. Most often not noticable and they don't see it. After a couple or-rings and tries they get tired and RTV the tube into place. OK until you need to remove the tube.

Make sure the Tube isn't bent or cracked and get a good O-ring. IF it still leaks you can either slather it with RTV or some people weld the end of a GM tube in place of the Mopar tube and use the GM seal. If it's a small block you can use a Tube from a Magnum engine shortened as needed. The Magnums already use the GM seal.