Jordo , one thing just dawned on me ,your symptoms sound to me like differential backlash common to 4wd vehicles .
they have a front , centre and rear diff and sometimes they are not always in harmony .
I have experience a few subtle shudders through the X5 whist rolling to almost stop then applying power .
I had an Audi 4wd do similar and a Toyota Landcruiser Amazon give very bad shudders at times .
maybe all this is a non issue .