Music (flac) playback issues

first and foremost I would like to thank you for the great piece of software, OSMC really is fun to use.
Although there is one problem I have since upgrading from Raspbmc:

while listening to FLAC-files there are audible delays, appearing a few times while listening to the file. This appears no matter what FLAC file I’m listening to and wasn’t the case in Raspbmc.

Because of that, it shouldn’t be a problem with the hardware or the connections (nfs or hdmi), an in my opinion it shouldn’t be a problem with the network bandwith (I’m using a wired connection to a nfs server), since all full-hd mkv videos including the audio run smooth without issues.

I discovered the following line in the kodi.log debug file every time the issue is audible:
15:55:46 1618.779053 T:3003118624 NOTICE: CAESinkPi:AddPackets Underrun (delay:0.00 frames:2205)

What does this mean, and is there a way to solve the problem?

Thanks in advance.

Here are my specs:

Device: Raspberry Pi B
Installation media: SD Card
Connection: Wired
Power Supply Type: ???
Power specs:
Peripherals: USB remote controller
Storage Device (incl. Network Sharing Protocol): NFS
OSMC version: VERSION_ID=“2015.07-1”
XBMC version:
21:05:13 17.772394 T:3023782448 NOTICE: Starting Kodi (15.1-RC1 Git:Unknown). Platform: Linux ARM 32-bit
21:05:13 17.772581 T:3023782448 NOTICE: Using Release Kodi x32 build (version for Raspberry Pi)
Codecs: mpeg2, vc1
Audio/Video Output: HDMI connection to Denon AVR

If you need more information, please let me know.
Thank you.