When you fill the Heart Action Strip with lights (a full Coherence Score) a bright light will be added to the bottom of the Heart Action Strip and the cycle will start all over again.
If, shortly thereafter you slip back to low coherence, the unit will subtract any lights that you have gained since filling the Heart Action Strip and continue subtracting until you regain a higher level of coherence, then it will begin adding lights again.
If you are close to the top (a full Coherence Score) you will hear the reward tone/chime again and a brightly lit light will be added to the Heart Action Strip again.
It will keep repeating this action until your score is high enough for you to be able to slip into low coherence with enough time to regain a higher level again. This phenomenon may happen several times before you advance far enough.
This is a normal design function and is not indicative of a defect or abnormality of the emWave device.