The MCH is a light duty cloud storage device with predominately SMR hard disks which have an average life expectancy of 2.5 year with constant use.
The reply on this subject of replacing hard drive has been consistent from WDT support staff over the years, there is no option for field (home) replacement of HDD for the MCH.
Most of what you see and search on the internet about MCH HDD replacement is incomplete or wrong.