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SanDisk's Name is Now Mud
(petapixel.com)
This is a most excellent place for technology news and articles.
My sandisk ssd also said it's "healthy". If it shows abnormal behavior for now reason it's getting faulty. Expected heat (like a good data transfer) is not abnormal but my problem happened with every data transfer.
Both CrystalDisk and the Sandisk tool said it was healthy. Took me 2 or 3h to fully transfer about 250gb from my ssd to my new one.