Dining Out - Who pays when there's a conflict over checks?

Since A specified separate checks two times (the first and last requests), and B only asked for a merged check once, I feel the waitress made a mistake. It's annoying; but, I would not spend time stewing over it.

Oh for gods sakes! I see this all the time when I help my friend out at his restaurant (hostess) . I feel sorry for waitresses who have to track multiple guest checks at one table. People buying each other drinks, splitting dinners, buying a round of drinks, etc. etc. hits a nightmare for the server who is trying to keep all these meals entered into a computer at the same time to the kitchen.

A said separate checks but B said he was picking everything up. That was the last order heard. The ball was rolling at that time. I really doubt if A's request was acknowledged again. A gesture of Generosity trumps a clerical mess.

When the check came A could have thrown two twenties, or whatever, into the center of the table and say, "i insist."

This stuff can get to bother one, especially is one is living a low money life for a bunch of time. I remember going to a landscape architect student (or were we past that?) group meeting and us splitting the check, let's say twelve of us. I sailed in late and just had coffee and a small something I don't remember now, since that was over thirty years ago. Someone at the other end said let's split it and there was no dissent.
Should I have spoken up?
I chose not to.
I might still have not, in the same situation, if that happened now.
The weird thing is that I remember this, and I liked, well, more or less, all those people. I think it was a financial blow that affected me that week or month, and I internalized it or my brain did.
This is a stupid thing to remember.. funny how some stuff sticks.

Another thing is when the owner picks up the tab - but what about the tip? I think the benefitted person should leave the tip. I have encouraged the owner to say. "Your dinner is on me. Just tip your server."

no and no

Party A should have left an excellent tip for the waitress for putting up with the crap at that table.

if it was a matter of life or death, Party A should have taken care of their bill immediately after ordering .

What is Party A's very good reason?