Hi,
I've a GB-BXCE-2955, https://www.gigabyte.com/mini-pcbarebone/gb-bxce-2955-rev-10#sp with current BIOS etc. The embedded NIC is a Realtek RTL8111G.
I've been running LE8.x on it for more than a year with no problems.
I update installed to 9.0.0 on day 1 and immediately hit problems with buffering on video playback. I also had a few plug-in issues and other problems (HDMI overscan re-calibration would be lost on reboot and the resolution reset to 800x600). I downgraded the install back to the latest 8.x and the problems went away immediately.
I left it until I could clean re-install, which I now have. 9.0.0 from the USB creation tool. Got it installed with no problems. Most of the problems went away, apart from the buffering/stuttering. Playback from SMB sources would usually stop to buffer in the first 10 seconds and then stop to buffer again every 10 minutes or so.
NIC is up and is up at Gigabit speed at the switch. No cabling or switch changes between 8.x and 9.0.0.
I tried to create an advancedsettings.xml with cache settings and this helped a little, with the initial 10 second pause remaining, but later buffering interruptions moving to every 15-20 minutes, but still very much there none the less.
My next step was to plug in a USB 3 Gigabit NIC (Dell branded). I rebooted and.... no buffering problems. It has been perfect all evening. Same cabling, same SMB target, same install, same config.
It looks like there might be a compatibility issue between the 9.0.0 build and the driver being used by the RTL8111G.