I was having high CRC errors and the SMART disk warning on the "old" disk2 before it failed, which is why I just removed / replaced it.
Parity2 has been my (only) parity drive for a long time now, since the last time I upgraded my parity to a bigger size.
So yes, I'm currently doing a parity swap, following the procedure here to the letter, essentially a physical swap of the 6TB (disk2) that had failed with a new 12TB. I unassigned the failed 6TB disk2, assigned the prior 10TB Parity2 to disk2, and assigned the new 12TB as Parity2. I stopped the arrays, powered down, etc when needed per the procedure steps.
I used a new SATA cable when swapping out disk2 so that shouldn't be the issue. No errors in Main, screenshots attached. Any thoughts?
EDIT: and for the record, I only bothered with the 12TB / parity swap route instead of just replacing the failed drive with a 10TB was because Best Buy couldn't locate the three 10TB's they supposedly had in stock, and gave me a 12TB for the same price. I didn't overcomplicate this intentionally.