Chosen Solution
Sounds like you wore out the 128GB Fusion blade drive. Being so small in size makes it susceptible to be over written to the point of failure. How many times can you bend a coat hanger before it snaps? Flash chips are no different! You can only write to the given cell so many times. To extend the life of the Flash wear leveling is done and there are also spare cells held in reserve to back fill. Now how full and how constant the drive is written to impacts the drives ability to wear level the smaller the drive the less it can be written to. So… you need a new blade SSD and get one which is larger like 512GB or 1TB in size. Here’s the needed guide iMac Intel 27" EMC 2639 Blade SSD Replacement
