sound distortion in zerberus

Hi, what could be the reason of sound distortion in sample https://youtu.be/rY-zQRW9YF0
and how to get rid of it?
sfz used has 26 wavs - two mono wav's for each line.
The same thing with similar sfz with 13 stereo wavs - one for each line. You can hear it in sample https://youtu.be/icq5ML2QT9c
You can hear distortion even in test sfz with only 3 wavs - https://youtu.be/TczFrldcysM
Moreover - sometimes I hear distortion just after clicking one note in a score - this or another.
I use notebook with i7 processor and windows 8.1. I also suppose that there is some influence of screen recorder but without it I here distortion often enough.

Next is a part of the 26-wavs sfz:

lokey=38 hikey=77
loop_mode=loop_continuous
ampeg_release=10

sample=samples\NMG_04-01_893geR.wav
lokey=38 hikey=38
pitch_keycenter=38
offset=0
end=959519
. . .