MPQ7225 - Problem occurring when the number of serial LEDs per channel differs

I am using the MPQ7225A and controlling all LEDs on all channels by controlling channel 1 using the Global Dimming method.

Three LEDs are connected in series on channel 1, and two identical LEDs are connected in series on channel 2.

When in operation, the channel with 3 LEDs is bright and the channel with 2 LEDs is dark.

VBIAS is 6.95V and ISET is 8.6Kohm.

What could be the causes?