KMP 188.8.131.52 is installed with default settings on win7sp1x86.
Open mp4 video file encoded with h264 and contained several audio tracks encoded with aac-he profile (sample file).
If change audio track by pressing Ctrl+X playback slows down. Issue could be reproduced not at once then try changing track again.
P.S. If the bug is confirmed please make proper report at BTS.