I am not aware of any such setting on the PSR-E463. While this may be a sign of a defective keyboard, it is more likely just the way you are playing your left hand easy-play chords.
As you probably know, the E463 does not have multiple easy-play modes -- it has a single auto-accompaniment mode, and it determines the chords or easy-play mode by the notes you play. For example, if you play a single C note, the keyboard can sense that you're doing "single-finger" chords (I put "single-finger" in quotes because minor, 7th, and minor-7th chords require additional keys to be played at the same time), and it will play a full background accompaniment based on a C major chord. But if you play the actual notes of the C major chord (C, E, and G), then the keyboard senses that you're playing an actual C major chord, not just a single note or cluster of keys, and it plays that same full background on a C major chord. There are multiple types of chords that the keyboard can recognize in this way.
Now, knowing that, if you have auto-accompaniment on and play a C note, you get that C major chord background. Now, let's say you want to next go to a G major chord background -- you'd then let go of the C note, and then play a G note to get a G major chord background. Now, if you accidentally play that G while still holding down the C -- even momentarily -- the keyboard will see you playing the C and G together, and it will give you a C5 chord, which is like a C major but without the middle E note, so the background sounds very similar to that of the C chord, and even after you lift your finger off the C and keep on playing the G, the chord background won't change -- it'll keep playing that C5 background (which you got by momentarily playing the C and G together in this scenario). You actually have to lift your fingers off the left side (accompaniment side) of the keyboard and then hit only the G again to get the keyboard to play the G major background, making it seem like the keyboard did not notice your chord change until you hit the key again.
In other words, for certain kinds of single-finger chord progressions, when going from playing one key to another to change the chord, if you accidentally do not fully release the first key before playing the second, the keyboard will interpret those two notes momentarily played as a chord, and will continue playing that same chord even after you lift your finger off the first note. To change background chords when using single finger/easy-play chords, you want to make sure you fully lift your fingers off of all the notes you're playing for one chord before playing the next.
Note that this is how the auto-accompaniment works on my PSR-E433. I suspect that the E463 works the same way.
