@whitey Glad to see you’ve made some progress. Got to be quick so will have to be brief. Replication was working but we suspect that some recent upstream updates have upset things as they appeared shortly after the new replication stuff was put in. There is another thread which discusses recent problems in this area and mentions the same error at least at one end as you are getting.
If you refer back to an earlier post of mine in this thread there is an explanation of the Big Red serial warning that I highlighed with a “N.B.” Not being funny just brief (just give the drive a serial number) And in answer to another question of yours I believe the command used to wipe the drive is wipefs. Also in the same N.B. post there is reference to wiping the drives with the rubber icon.
Sorry got to dash now. Well done on persevering and sharing your findings. We are not there yet obviously but I am firmly of the opinion that things are moving in the right direction.
Note that if you have to go through all that badblocks business then things do seem a little strange with your drives.