In order to narrow down this issue, would you please try the following step below and keep us inform about the result:
1. Make sure the firewall on the DiskStation is not blocking any ports. Do this by going to DSM > Control panel > firewall > ensure it says “if no rules are matched: allow access” at the bottom of the page, and save the firewall rule.
2. Please click the "re-index" button to re-index the media files on WebUI > Control Panel > Media Server > Index Folders.
3. Please uncheck all setting under DS UI > Control Panel > Media server > "Browsing Settings".
4. Please disable MIME under DS UI > Control Panel > Media server > "DMA compatibility".
6. Please kindly setup your media device profile to be "your media device" on WebUI > Control Panel > Media Server > > "DMA Compatibility" > Device list.
7. let your media device and DiskStation with the default setting of 1500MTU, afterward connect DiskStation directly to a your media device using an Ethernet cable without going through a router.
8. Can you please check if there any problem when attempting to UPNP renderer the same media files via a Windows PC using Windows Media Player and twronky and XBMC ?
Could you please let me know what is the codec format of the media/audio files which could not be played? Please use the "Media Info" software to retrieve the codec information. (Please use the "tree" view)
http://mediainfo.sourceforge.net/en
If problem persists after setup all above, please send us a copy of your kernel log and DMA Log, the instructions have been mentioned in below. The Kernel log is a technical log file which can give us more technical information about your system
1. Login Management UI
2. You can see the similar link
http://192.168.xx.xx:5000/webman/index.cgi
3. Add ?diagnose=debug to the link, like
http://192.168.x.xx:5000/webman/index.cgi?diagnose=debug
4. Press "Enter", then the file can be downloaded.
[DMA Log]
Please refer to procedures below to retrieve us a DMA log message for further diagnosis.
a. Log in to Management UI > [Applications] > [Media Server]
b. You will see option [Diagnose] in the bottom of this page.
c. Click [Diagnose]> enable [Enable DMA communication log for diagnostic purpose]
d. Reproduce the DMA issue again and do to [Diagnose]>[Download] to retrieve the DMA log.