Plex is buffering locally played files from OMV Nas

Since I have moved my video files to OMV server, I am constantly buffering using plex media player on my HTPC. The videos are all being "direct played" which means no transcoding. When I test the speed between NAS server and HTPC using iperf I get around 300 Mbits/sec mbps (~36MB/s) which should be plenty. But when I watch the network traffic on the server, the HTPC is only pulling around 10-20 mbps. Everything is hardwired. I have the same problem on a different computer. When I play the file in windows media player on the HTPC, I dont get any buffering! What could be causing this?

To be clear, OMV server holds the files, the HTPC is where Plex Media server is and it's libraries are pointed to the NAS through a mapped network drive with drive letter.

Please help if you can, thank you.

I realize after researching this all yesterday and today I didnt provide enough information:

PC OS: Windows 7 on HTPC and Gaming PC (GPC), OpenMediaVault (OMV) 3.0.96 on file server

I did some speed testing and found out that the network transfer speeds while playing the video weren't fast enough to keep up. BUT every other transfer speed measured not using Plex seem more than adequate (see table of speed tests below). I tried bypassing the switch between OMV and HTPC, I tried turning the firewall off, I added the extra options to the SMB shares settings, but nothing seemed to work. But when I bypassed the OMV server and played the same file from either the HTPC or GPC, there was no buffering when playing on the opposite computer!

So something must be slowing the connection between the plex media server on HTPC and OMV server as the video is being played. I just don't know how to fix it.

I tested multiple methods of playing my best video file through my network. I copied the file to the other 2 computers for testing. In the table, "Server" is where the file was streamed from and "Client" is the PC client I played the file on using Plex Media Player. All OMV speeds are measured using "bmon" or iperf, the windows computer speeds were measured using iperf or resource monitor.

All speeds are MB/s (not mbps)

*Very inconsistent

OMV = OpenMediaVault Server, where video files are stored by default
HTPC = PC where plex media server is running and where I am trying to play the videos through Plex Media Player
GPC = gaming PC used for troubleshooting

Network Map:
OMV --> switch --> router 1 --> modem
OMV --> router 1 --> modem
GPC--> router 2 --> router 1 (~150ft exterior cable) --> router 1 --> modem

I am not really sure what is causing the speeds to only be low while trying stream the file from the OMV server to the plex media server on HTPC. Can anyone help? I will gladly pull any other info or logs needed