tornado_blade's point is valid, but not expressed perfectly, the error in the kernel log could be the result of a mix and match of hash boards, but it's not always the case, especially given that OP mentioned the miner is brand new, so to be an EEPROM issue is just unlikely.

For your case however and since you know your boards are good and this started after mixing them, then you have two options.

1- Get a tool that allows you to change the EEPROM code, like this one > https://www.zeusbtc.com/MinerDetails.asp?ID=236
2- Use custom firmware like Vnish which ignores the EEPROM altogether.

The reason why you can't mix and match these boards is because they come pre-loaded with voltage settings (and maybe a few more things), the official firmware will check to see if they all match, if not, you get into an issue, so using the tool above or anything else that does the same thing, you can just copy the settings from one hash board and paste it on all other hash boards, that way the official firmware will think they are the same and will work just fine.

The "cheaper" method (but you have to pay firmware fees) is to use custom firmware like Vnish which ignores all that and lets you mix and match hash boards, which option is better? I don't know,  it's 2-3% of your revenue is $200 paid once.