Thanks for confirming that suspicion, I am glad I never did that then. Not least because it has started working again.
By coincidence I had System Information open with both the broken and working MyBooks connected and noticed they had different firmwares (broken on 1014 and the other at 1015). Feeling I had nothing else to lose I downloaded the WD Firmware Updated to see if that would help. I was hoping that maybe the firmware could have been corrupted, or there was something in a new version that would specifically fix my problem.
Although the updated detected a new firmware of 1017, it gave an error while trying to write it. Despite that the unit still showed in Finder when connected so it did not appear to do any damge (and System Information still showed firmware 1014) so I thought I would check it again anyway. It seem to work beyond the point where it had been crashing, so I performed a surface scan on the whole disk to test it. These seem likea good test because as well as ensuring the disks are accessible, it keeps them spinning for several hours so any heat or interface problems should be highlighted. These had been fialing after just an hour, but with both USB2 and FW800 connections it got through the whole disk with no issues. Verifying the data on the MyBook with a copy on a backup drive has also been successful, with no crashes nor any signs of file level corruption.
I am not sure how failing to update the firmware could have had this effect, but it is the only thing to change after several weeks of unsuccesfully trying to test and resolve the problems. But given my subsequent testing has been far more intensive that the unit would ever experience in normal use I feel confident to resume using it.
So if anyone else encounters the same problem in future, my advice is to just run the firmware update from Western Digital’s product support page and see if that helps.
