I think I may have a similar problem with my Freelander.
It is forever blowing brake light bulbs on either side and has done so for about 2 years. When you look closely at the bulb when it is removed from its holder, the contact bars that the element joins appears melted, so there is clearly something wrong. Despite trying a number of different makes of bulb, the same thing happens each time. There are no signs of water ingress or condensation in the lamp unit and the contacts are clean.
I did speak to the local Landrover dealer about the issue and he had never come across it before, so could not offer DIY advise.
I would be interested to hear if anyone else has had a similar issue, good luck with yours...
Rgds
Col