Hi. My name is*****'m a camera repair technician with almost 30 years in the business and I'll be glad to help you with your question today.
The best thing to do is download all the images and then re-format the card in the camera. This will give you the most room on the card.
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It sounds like more than a formatting problem. There's also something electronic going on as well. Repairs usually run $100+ so you may want to consider replacement rather repair. There are a lot of them on the market in that price range.