[blindmule]

Don't bother with the dealer.

You need a thin strong plastic piece about 10cm x 5cm. I used a safety tag from a children's car seat. Like the ones from a new mattress or a sofa. It needs to be thin and strong.

Tilt the seats way back.
Take the headrest off.
Both holes have a horizontal pins.
Fold the plastic piece in half length wise twice so it's about 10cmx1cm.
Put the plastic in the hole half way by the pin that does not have the release button.
This will block the teeth of the headrest from engaging the pin.
Put the headrest poles back. Push the button and slide all the way down.
Pull plastic out. Voila!

Do not use a metal tool as it may scratch your bimmer. Do not use thicker plastic as it will create too much pressure. A chip bag wrapper will likely work. The material should not tear or strech easily.

I'm 5"9 and am more comfortable with the headrests all the way down. Thanks RxCritical for guiding me to the fix.