There is a very similar problem here, and a solution. SSD in a MacBook Pro (mid 2012, 13"), Finder symbol with question mark. You need a new internal SATA disk connector cable to work with the new SSD. I have encountered the same problem with my MBP mid-2012 and a new Samsung 860 EVO SSA.
My macbook Pro was almost unusable because of kernel_task high CPU for weeks
At the same time the battery get inflated so i finally decided to go on Apple Center in Rome to replace it... even if out of warranty Apple have replaced my battery (and keyboard as well) for 0€ cost.
Even better ... kernel_task problem suddenly disappears !!!
so i'm pretty sure ...