EDU06 LEDS not blinking alternatively when connected

EDU06 instructions under section 5 state "Once powered, the LEDs (LD2 & LD3) should blink alternately. The board is now ready to perform experiments".

When I connect mine to the power adaptor the LD2 and LD3 flicker at the same time, not alternatively - why is that?

The speed of the flicker can be adjusted by turning the knobs.