2000 Boxster key off battery drain

Hello,

There is an unexplained battery drain on my 2000 Boxster.  When I connect the milliampmeter, the reading stabilizes at 12 mA after a few minutes of waiting. 

However, when I open and close a door, the reading will not return below 100mA, no matter how long I wait.   Disconnecting and reconnecting the meter, for just a second (opening the circuit) and the reading stabalizes at 12 mA again.  This happens every time.

I removed the fuses, one row at a time, repeating the same measurment procedure each time.  Then, I replaced that row's fuses and did the same with the next row, etc.

I was unable to get rid of that  pesky 100mA drain.  I do not always have access to ac power to rely on a trickle charger .  Somthing seems wrong so I would like to fix it.

Your suggestions are most welcome and thank you for your help.