How would you handle this situation?

New setup at a new location.

2x ASA 5506 in failover. 2x Catalyst stacked. Plus other stuff not relevant to the story.

In my assembly instructions; ISP equipment connects to a random vlan and then 2 ports go to each ASA for the high availability.

The onsite contracted 3rd party sent a tech who would not assemble it that way, "Internet connections cant be plugged into the switch." They plugged the WAN directly into ASA1. I let it slide because I needed other work completed. We have full remote access to both ASAs.

Now after the fact we needed that fixed. It was assigned to my coworker to get it cabled correctly and test.

My coworker did not fix the cabling state and instead tested the failover which didn't go well.

My coworker proceeds to go to our boss and say that my configuration on the firewalls are so bad that they need to be both shipped back to us(internationally >5000km away) for him to reconfigure them from scratch. My boss updated me about this because I am the one responsible for these devices.

So I emailed said coworker that the cabling is not plugged in correctly. I only provided facts directly related the cabling issue.

His response back to me was that he told the bosses that 'the configurations are totally not the issue' even though I never brought it up.

So basically the boss or him are lying.

I replied back, "Why do you need to bring them back here? We have full remote access to them."

His response back was, "I want to make sure the chips are clean. I saw on one of the forums that dirty chips can mess with performance and I don't want them opening up the units to do it themselves." That's literally copy and paste of his response.

I forward this to my manager but not the boss. I said, we should trying plugging the cables in properly first. My manager's response was more or less that 'You were warned to make my configurations like his otherwise I will upset him.'

TLDR: Coworker is going to our boss, telling them that I'm bad at my job and he needs to do major amounts of work to fix my mistake. But I'm being told it's my fault for upsetting him.

That's where it stands. How would you handle this?