I have created a support ticket (#5958) for this a few days ago (no response, yet).

Here’s a 7zip with some audio recordings (with + without bug), the samples used, and a textfile that describes the issue (and how to reproduce it):

http://www.mediafire.com/download/lf0adeio3lzt1t8/ar_sample_start_bug-23Jul2014.7z

I’m convinced that this is a bug, not a feature.

It probably has something to do with improperly reset internal sampler engine states, and it might be related to the “clicking samples” issue (ticket #5959).