How these two meet
The argument you keep almost having is about fairness, and the reason it never lands is that you both believe you are on the same side of it.
Libra means: nobody in this room should be carrying more than they can hold, and I will adjust things quietly until that is true. Aquarius means: the rule applies to everybody, including the people we like, especially the people we like. Both of those are fairness. They give different answers about once a month.
Venus weighs. That is the entire activity: what is this worth, what is that worth, how do the two get level. Saturn does not weigh. It decides and then holds, retrograde 36.4 per cent of the time and still arriving in the same place. So when Libra rebalances something Aquarius had settled, it does not land as kindness. It lands as the rule turning out to be negotiable, which for Aquarius is the same as there being no rule.
And when Aquarius holds the line on somebody who is struggling, it does not land as principle. It lands as a person being left uncomfortable when something could have been done.
For Libra, the work is letting one uncomfortable thing stay uncomfortable, unsmoothed, for a whole day.
For Aquarius, the work is naming one exception out loud and calling it an exception, instead of pretending the rule had covered it.
And a third: you are not going to agree about this. What you can stop doing is each assuming the other one got there lazily.
The question
Which one of you decided what fair means here?
One conscious action
one exception, named
Next time your two versions of fair produce different answers, each say which one you are using before arguing about the outcome.
You will still disagree. It stops being an argument about character, which is quietly what it had become.
Venus adjusts until nothing is out of balance and Saturn holds until the line means something, and neither of those is the soft one.
Between you there is always one person who ends up carrying the discomfort, and the two of you have never agreed on who that should be. What neither of you has ever done is stop arguing about it.