On 09/06/2022 01:25, Alan Braithwaite wrote:

Appreciated.  Only reason I didn't include it initially is because it's a giant wall of text (which the other debugging info was anyway, so I should have just been proactive).

Anyway, it can now be found below, annotated with the failing drives first.

The thing that jumps out at me from that is while SMART is available and 
enabled, it should list a bunch of SMART settings, including SCT/ERC. I 
can't see that. That's worrying.

A quick google also says these are old drives, which may or not be a 
concern. That also possibly explains the lack of sct/erc.

Given that you say three drives all failed in the first slot? My money 
would actually be on nothing to do with raid, but a dodgy cable or 
motherboard connector. I don't think they're rated at being swapped over 
that many times ...

I don't know how much help this website will be for you, but take a look...

https://raid.wiki.kernel.org/index.php/Linux_Raid

You've already done some of what this asks for, and I don't actually 
know that the rest of this will be much use ...
https://raid.wiki.kernel.org/index.php/Asking_for_help

Cheers,
Wol