HELP! Firmware update to WD Black 2 (Dual) to 01.01A02 causes extreme slowdown of disk I/O

WD Internal Drives Desktop & Mobile Drives
3

I have analysed the firmware update and AFAICT it targets the HDD but not the SSD.

Analysis of a Western Digital firmware update (for a different model):
http://www.alexsoft.org/viewtopic.php?f=59&t=776&p=2807