That sounds like a problem where the hard drive isn't able to keep up with the note streaming. Do you have an SSD in your macbook by chance? Some of the older SSDs were notorious for randomly delaying write and read requests by a large fraction of a second (or even more than a second), despite having tremendous averaged performance over time. Perhaps even some new SSDs do this to a lesser degree, I'm not sure. But a delay of even 200ms might be enough to cause drop outs.
Thanks for the fast response Jeff, I truly appreciate it. No ssd here, but the hd/streaming theory is still a good one; my older imac has a 720rpm drive, the macbook has a 5400rpm, that might explain why an otherwise faster machine nevertheless has issues.
I'm going to move the samples to a fast external drive, I'll report back.