I'm somewhat certain that this is in reference / related to an earlier event from a year ago:

    https://forum.promise.com/thread/let-s-hope-this-r6-survived/

While the unit has appeared to function without event for the past few months, in the last month the slot in question appears to have now fouled two drives -- the latter significantly newer and largely unused when it was mounted to replace the former. 

The fouled drives are so badly damaged that they will not mount on any other device, and make an awful "clunking" sound when my drive caddy attempts to spin them up. 

To be clear: both drives were fouled in Slot2, which is the slot that originally showed problems when the power spike described at the link above occurred. 

Am I now correct in not trusting this particular slot on the RAID?  Should I just continue running it as a 5-disk RAID instead of 6?

Here's a dump from the event log. Nothing interesting..

Event List at 2021-03-29 23:18:31 .

Index  Device ID      Severity    Time                          Event Id            Specific Data                                                         Description                                       

0      Ctrl 1         Info        Mar 29, 2021 23:14:14         0x00040005          000000000000000000 0000000000000000 0000000000000000 00000000000000   The system is started                             

1      SEP 1          Info        Mar 29, 2021 23:14:14         0x00060002          000000000000000000 0000000000000000 0000000000000000 00000000000000   SEP is found                                      

2      PD 2           Minor       Mar 29, 2021 23:14:14         0x000D0011          000000000000000000 0000012020202020 2020202020202057 344A3050433439   Command times out on physical disk                

3      PD 2           Info        Mar 29, 2021 23:14:14         0x000D0003          000000000000000000 0000012020202020 2020202020202057 344A3050433439   Physical Disk has been reset                      

4      PD 2           Warning     Mar 29, 2021 23:14:14         0x000D000B          000000000000000000 0000000000000000 0000000000000000 00000000000000   Physical Disk has been removed                    

5      LD 0           Major       Mar 29, 2021 23:14:14         0x00090004          000000000000000000 0000000000000000 0000000000000022 E30001551E3A0C   Logical drive has been set to critical