Video located on NAS pauses after a few seconds

New to Kodi and hoping for some insight on what might be the cause of playback issues with certain video files.

The main type of file I’m having trouble with is GoPro .mp4 recordings. Some are 30fps, while others are 60fps. Problems with both. These videos begin playing immediately and then playback pauses after only a second or so. After a long delay, playback sometimes resumes or resumes at high-speed, as if someone pressed fast forward. Other video files from camcorders, etc. have no playback issues.

All files are located upstairs on an unRaid server and stream to Kodi via powerline ethernet. My Kodi box is fresh Windows 8.1 install on a i3-550 desktop PC with 4GB ram and SSD hard drive. This is a dedicatd HTPC machine, so there no other software installed other than Kodi.

Information from pressing “O” and “I” keys shows throughput of 30+Mbps at the Kodi box. When playing a file, the flow of data from the NAS drive to Kodi begins at ~30Mbps. A second or two later, the transfer rate drops to zero, at which point playback is frozen. After staring at a frozen screen with zero throughput (for anywhere from a few seconds to a few minutes), data flow resumes at ~30Mbps. Does anyone know what could be causing this pause or the drop in the flow of data?

PS- I’ve tried already tried changing the buffer settings via Easy Advanced Settings. Nothing seems to help with the GoPro .mp4 files, but as I already mentioned I don’t have any issues with video files from other sources.