I may have missed it, but I don't think there was mention of running scandisk on the apparently wayward drive. If it was run what were the results. If it didn't find lots of errors then the problem is probably soft, ie the file system has incorrect information in it. Did scandisk fix this or not?

Google's research using 100,000 disk showed that SMART was useless at predicting disk failures. It did agree with much of what has been said here

- Once a disk starts producing errors it is going to fail and fairly quickly.

- Disks older than 3 years have a high risk of failure - 1 in 10 per year.

They also found 5% of disk failed in the first few months.

The most significant finding in the context of external drives if that cold drives fail more often. A drive at 15C is 6 times more likely to fail than one operating at 37C. Following the trend of their graph would indicate colder would be much worse.

I would deduce from this that external drives should be kept in the warmest place in the house. If the drive has been in a cold place let it warm up in the warmest place available for a couple of hours before using it.