When you measured the parasitic current drain on this car, how long did this test last ?
I had a similar problem regarding a Fiat once, where the battery couldn't hold charge and where the battery have been changed multiple times.
The only tools I had to diagnose this Fiat, was a DMM and a current clamp. I did not check for ripple voltage at the battery as I was focused on the parasitic current drain this car had.
One of the first thing I did to insure that it wasn't some accessory there were making the parasitic current draw and I concluded that there were no.
It's here the strange part of my diagnostic begins. With the current clamp around positive cable at the battery I see no amps readings. I then put DMM in series with positive cable,and now I get a reading at around 80 mA which seems alright.
Then I turn on the ignition key a couple of times and suddenly when I was observing the amps reading at the DMM it begins show a reading of around 8 amps. Then I do the same test again which just confirm the what I have seen.
The high amp readings are first present after 5 minutes. My focus are then on the alternator as this part are connected to power all the time. I put current clamp around positive cable at the alternator and repeats the test from above.
A new alternator corrected the parasitic current drain this Fiat had.
I am not saying its the same with your car but you should check this as well.