I found during a fight that one of my characters had 2 reasons for Disadvantage and 1 reason for Advantage on an attack. This resulted in the final attack having Disadvantage. It's my understanding of the rules that it doesn't matter how much there is of one vs. the other, they always cancel out.
So if there were 4 reasons for Disadvantage and 1 for Advantage, the attack roll should be a flat roll with neither. Same on the flip side for having multiple reasons for Advantage and only 1 for Disadvantage, it would be a wash.
Not sure if this is a bug, an intended design choice, or my failure of the rule interpretation