Sometimes my '04 will do that, but in my case it's operator error.
That is,
Often times I'll attempt to slow down using only the Regen but not depress the pedal so far as to engage the brake shoes.
I'm in effect riding the edge of the brake switch, keeping regen ON.

Sometimes I'll (Not knowingly) back my brake off and loose the regen activation for a moment- then my foot "bounces" back on it, turning it back on.

When it comes back on I'll be traveling at a much slower speed than before so it comes on with only 4 bars CHG.

Does that make sense?
I'm not sure if your case is simialr or not.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT