I have had several kettles where the lid mechanism eventually fails. None of them have been the make you have but I think it's a common problem with many types.
They don't make kettles to be easy to dismantle and I think the lid issue may be caused by a gradual build up of limescale on the release mechanism.
You might try using Citric Acid powder - Amazon or Home Brewing shops. Mix up a solution in the kitchen sink and before retiring plunge the kettle lid first into the water.
Citric acid is excellent for descaling the inside of the kettle and for sprucing up the inside of a dishwasher too.
Good Luck...
January 2017
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