Thanks for taking the trouble and addressing my request.
It is actually not the autosuggestion drop-down window, it is indeed the terminology recognition window. That is, the window where you can either search for terminology or where terminology found by SDL is shown in the list. I find this behaviour really weird and I have found so far no solution in the Dragon settings.
Yet it is probably a good idea to deactivate autosuggest – which I do not use anyway because it is useless for me as a dictator :)
I will let you know on Monday when I go back to the office.