When doing advanced dictation, it is sometimes impossible to hear the difference between the melody tones and the chord tones. This happens often during longer note values because the melody tone is also played as part of the chord. This could be fixes if the chords were played by a different sounding instrument perhaps.
Also, when the melody is playing a non-chord tone, it can easily be interpreted as the 7th of a chord. EX. “Re” in the melody with a IV chord underneath sounds the same as a ii7.