4K HDR Content Buffering In-home Streaming

[ToxicBatosss]

So I have a Plex Server setup on my Desktop PC (Ryzen 7 3700X, 16GB Ram, RX580, Intel Gigabit Ethernet)
My desktop is wired with Ethernet cable to my router (UK Virgin Media Hub 3 Router), and my TLC C71 TV is wired to the router. Everything is wired.
When trying to play 4K HDR content (files around 25GB), the playback buffers on my TV every ~30sec. Normal 1080p content plays fine.
Looking at task manager, my CPU usage ranges from 60-90% when streaming said 4K content and the upload speed from my PC ranges from 30-50Mbps.

What I’m I doing wrong? Most of the Setting in Plex server are set to default, Direct Play ON, Direct Stream ON, Transcoder set to Automatic.

Any Help? Router Bottleneck?

[FordGuy61]

@ToxicBatosss

my CPU usage ranges from 60-90% when streaming

Plex Media Server version?
Plex Client version?
See Authorized Devices.

Is the video transcoding?

Check Plex Dashboard → Now Playing. It will show if the video or audio is transcoding.

[ToxicBatosss]

Everything is up to date, I always keep the server/apps updated.
Weird, this time my CPU usage has been almost none.

[ToxicBatosss]

Forgot to add, all my media is on a Seagate 2TB USB3.0 External Drive, while streaming the read speed reported in task manager from the drive is 5-10MB/s.