Looking at your question, I can say that most astrologers look only at Ashtkoot guna milan and do not dig deep into astrology charts, and that is why despite a very good ashtkoot guna milan score, problems in marriage do take place.

Do note that Ashtkoot Guna Milan is just the First Step

Understanding Ashtkoot Guna Milan:

The 36-point system (Ashtakoota Milan) mainly assesses compatibility from Moon. Depending upon the placement of the Moon in the birth chart. I mean rashi and Nakshatra, this system calculates a score, but do remember this is not complete horoscope matching.

Individual Horoscopes Matter More
While Guna Milan gives a quick compatibility snapshot, each person’s birth chart must be examined in detail: For example, a person’s individual chart could have divorce yog, seperation yog, that has not been checked in Ashtkoot guna milan. Also, an individual could be running 6th lord dasha or 8th dasha or 12th dasha or dasha of a planet placed in the malefic houses. So in this case, the divorce yog may not be there, but dasha of 6th, 8th and 12th could impact marriage, leading to divorce

Studying of Individual chart can show signs of marital challenges, separation, or Doshams (like Mangal Dosha), Rahu dosha, Naag dosha etc? Weak 7th house, lord and Karka, which will not be revealed in guna milan.

Your 28/36 score shows the match had strong potential. But if deeper planetary positions, dasha periods, 7th house and lord and dosha in an individual chart aren’t favorable, challenges on the marital life could still arise. So it is very important to get charts matched before marriage from a good astrologer and not from online app, as they do not provide complete horoscope matching. A complete personal marriage chart analysis would offer more clarity on your relationship.