ear training question

I spoke to someone about ear training and he gave me an interesting method. I told him that I recognized intervals that involve the root but other intervals (we'll say) from the 5th to 3rd would throw me off. He said that he treats every note as a new root.

My ear is so used to the major scale that if I start on the root, I can sing a major arpeggio but if I move to the 6th I automatically sing a minor arpeggio when I am trying to sing a major arpeggio. In orer to sing it right, I have to forget the sound of the root and make the 6th the new root in my head but this takes a very long time. I have been doing it for a while but it doesnt seem like I'm making any progress. Any advice on how I can be more accurate with my eartraining? hopefully someone has some tricks or tips they use