cats has a fairly good set of repbot stats - and seems reasonable to me. My approach would be to tell or message him, asking what it was about you that upset him enough to complain. If you give a player the opportunity to tell you 'face to face' what bothered them, and take it courteously, they often wont feel like leaving the complaint there.
If it is something you don't normally do, like a bad connection that day..ask for the opportunity to play again, to prove it isn't a consistent thing.
If none of that nice approach works, don't get upset - you have a positive reputation - and that is all that matters. The reason repbot works at all - that so many players struggle with, is that a single opinion is not important. It is the collective opinion of many that makes a meaningful statistic.
Your rep as it stands would easily pass my criteria to play you - and I am a toughie
I have complaints from some idiots - but it doesn't bother me in the least - in fact, some of them make me chuckle