You need to find out where it's leaking.
Is it down onto the battery connection
through the air hole? Then maybe the flavor wicks are off, or the head has come a little loose. Many of the bottom coil units have that last issue - just taking it apart to fill can back off the head enough to cause a leak.
Is it leaking where the base screws to the
tank? Maybe a bad o-ring, or dirty threads keeping it not tight.
Are you attaching it to the battery too tightly? That can cause leaks.