How do I answer questions like "If you have ever been involuntary terminated, please explain" on job applications?

What exactly are employers looking for when they ask this question?

Like, okay, the last time I got fired (I assume being laid off like I was at the start of the pandemic isn't what they're looking for with this question, and previous firings are so far back in my job history I don't even include them on my resume anymore), it was for reasons that I still contend are kind of BS and cruddy management, and I like to think that employer got the karmic rebound for it since they went out of business not long after.

I was bartending at a restaurant when I got a call from my boss telling me not to come in because I was fired; she explained that customers had been complaining about my service and that servers had complained that I had gotten drink tickets mixed up. This was literally the first I had heard either of these complaints, and yet apparently they were big enough problems that they decided to give me the boot.

I've complained about this before (I forget what sub it was on, but it's somwhere in my post history if anyone cares to dig back to early last July), and people suggested that I was being whiny, and, fair, I was venting on Reddit after all. But what's the application-appropriate way to explain that I got fired for something I literally did not know was a problem until I got fired for it?

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