Audible "click" after importing new drums

I've been recording short snippets of sounds from my Boss Dr 550MKII. I've taken great pains to edit the files so that there is no extra space before the sound, to keep it in rhythm with the patterns. I've also edited out any extra space at the tail of the sound, making sure it fades neatly and cleanly. I am saving files as 16 bit mono aif files with no compression. When I build a new kit and import these sounds, most every one has a "click" at it's tail end. I've double checked all the files I imported by viewing and listening to them in an external editor. The original files are clean, with no "clicks" or "pops". I must therefore conclude that Doggiebox is somehow adding this "tail pop" as I import the sounds.