Constant Streaming errors



First timer here, so bear with me...

I have been running a Plex server on my iMac, and using a 3TB external HDD to store my content. It has worked very well for the past 2 years. I decided i wanted to upgrade my setup, and added a 4-bay Seagate NAS to my network, and picked up a Mac-Mini with the sole purpose of it running the Plex server. I have two 4TB HDD's running Raid1, and i transferred all my content over to the NAS. Now, when I stream content from the NAS, the movies and TV shows will time-out with a "network error" about every 5-10 minutes of attempting to watch something.

Any idea what is happening? The Mac Mini is hardwired to my network, and the NAS is obviously hardwired to the network as well. The NAS is simply a storage device, while the Mac Mini is doing the transcoding (at least that is how I understand it). What could be causing the movies and tv shows to not stream as well as they did on my iMac with a external HDD attached?

Seagate NAS model: STBP4000100