Chosen Solution
I have a Fledging Feather M13 512G SSD in my MacBook Pro 2015, it caused unexpected shutdown and restart many times. The MacOS version is 10.14.6. And the speed is low as shown in the attached image. And in the system information, the link width is x4 but the link speed is only 2.5GT/s. What is the problem and how to solve it?
Things I would try is to make sure the drive is not overly full as the wear leveling process could be struggling trying to prevent you from over stressing what few free blocks you do have from being over worn. Of course you could just backup your data and reformat the drive to see if that helps. Basically, your drive is too small for the amount of data you are storing. Smaller sized SSD 128~256 GB need about 1/3 of the drive free to work effectively, larger 512 GB ~ 1TB need 1/4 free. If you can’t get better performance It then sounds like you have a 2.5 GT/s drive not a 5 GT/s drive you where sold. I would return it and get a better drive.
Check if ccleaner is mac os compatable and check if there’s a ssd defragging tool within mac os and try running those.
