If it is a defect like foggynotion has suggested it is ( and I agree with him that it is. Not for all, but it has been for some, me included and I did look after mine and was very careful about never storing in a hot car boot or exposing for too long to the heat) you should be able to get it fixed by Minelab and it should only cost you to send it there and back if it is out of warranty.
From the following link , that I think is relative to US Consumer Law;
http://www.consumerreports.org/cro/magazine/2013/05/the-word-on-warranty-protection/index.htm
It says the following in part:
" What you should do. If you discover that something you bought is defective—even after the written warranty has expired—contact the retailer and manufacturer to ask for a repair, replacement, or refund. It doesn’t matter what the retailer’s return policy is or that the manufacturer put a notice on the box telling you not to return the item to the store"
I am sure Minelab will help.
All the best
David Di