I would think that kids that move around a lot (especially between countries) are a great deal more adaptable to local culture and are probably more attuned to the little idiosyncrasies of a region (including language).
It's strange that a short period in a couple of places stuck with you more than others. Is Carlisle a military town too? I was just thinking, maybe it's because military bases tend to be quite an amalgamation of people and accents, and that homogenised your language/speech in a way that wasn't specific to start with - that is, until you lived in places with more distinct and uniform dialects/accents. That might have solidified it for you. OTOH it could just be the age you were at that time is a more formative period for children in terms of developing speech patterns.
BTW can you still speak German or have you lost most of it?