I did experience this with a man. My Sun in 18 Aquarius and his Venus in 15 Leo.
I have loved him very much, and he loved me very much and we stayed together for about a couple of years. I met him last week after 20+ years not meeting. He said I have been someone very important in his life. I have a very sweet memory of our time together too, although it did not work. We are not even very clear why we separated, which happened smoothly. I am now only looking up at our synastry.
You wrote a few things that are not relevant, save this one:
The Venus individual complains that the Sun person is too unyielding and the Sun person has trouble appreciating the Venus person's tastes and values.
That makes sense and rings a bell in our case, to some extent only though.
But... we have conjoined Sun-Moon in Aquarius (5 degrees orb) that comes in the mix, difficult to disentangle from the Sun-Venus aspect. Otherwise, surprisingly his chart makes no major aspect to my Venus whatsoever, and my Sun opposition is the single connection to his Venus, which is quite impressive in a strong romantic story that was so tender and sweet. It's hardly believable. Our sexual life was also good, yet nothing involving our Mars either can explain the love affair.
I would say the Moon-Sun in the impersonal, intellectual Aquarius can hardly explain the gentleness, warmth and sweetness of the intimacy and the strong love ---and I would therefore include the Venus-Sun opposition as a support, because there is otherwise not much romantic resonance in the synastry.
But now, his Moon might be exceptionally strong, and thus her conjunction with my Sun be especially effective: he is born before sunrise by night, with his Moon near MC. I don't have his exact birth time, could be Gemini or Cancer. Now given the story, it could be Cancer, that would strengthen his Moon even more and make the conjunction even more effective. And his Sun is Cancer, so his Moon is very important in his life.
Of course if his MC in on my Sun, that would add effect.
The other remarkable thing in the synastry is his Mars right on my South Node (in Libra, maybe bring Venus in the picture through rulership?). I suspect that is binding. But not necessarily romantic (save the Libra tone?).
Other than this, I don't see any reason why we were so much in love. There are a few other nice things, but they could make for a mere friendship: loose sextile from my Jupiter to his Sun, and from his Jupiter to my Moon, and a bit and loose connections bringing our Mercuries in slight touch with each other's chart. With hindsight, and with our latest meeting in mind, I would say Jupiter was a great support.
So once again the entire synastry must be considered, and rulerships seem to be very important.
I can't say whether the Sun-Venus opposition eventually harmed the relationship --that's entirely possible, but I would suspect it brought us in each other's arms.
Any comments are welcome.