So I've had my 2008 Galaxy for six years with no real issues to speak of and have been happy with it. Recently I noticed water in the nearside inner tailgate light (larger unit with the fog light in), so removed it and thought it was the cause so bought a new unit, but it still got about an inch or so of water in it which would then partially drip out when the boot was open. I've since changed the foam gasket but it made no difference. I can't see any other point that it is obviously getting in through and would appreciate any advice or if anyone else has experienced this? Next job may be taking the trim off to get a better view if it is running down the cabling from the top. I asked my local garage to have a look when it was in for a service but they just suggested drilling a whole in the bottom of the light but certainly not ideal!

Finally found that the top brake light seal had perished and was letting in water that then ended up in the tail lights in the tail gate.

All sorted now with a new unit.