I had this on my front nearside light. Its worth checking the back of the light is actually clipped on properly to maintain the seal, they have a tendency to seem like they're properly seated when they're infact not. The nearside front is particularly tricky if you've got big hands, as there is not much of a gap between the back of the light and the battery, but it can be done. If they seem to be loose, dry out the light first before fixing. A couple of mins with a heatgun on low, or a hairdryer blowing into the back will do the trick. just don't melt anything nearby! No idea about the back lights, not had this problem, cant really go wrong in removing them anyway, and checking the seals.