HD Homerun see strong signal but plex complains weak signal

I’m using HD Homerun tool to see signal strength and it shows between 98 to 100 (100 max).
However, plex complains signal is weak recently. I do see pixelation on live TV but for one particular channel, the video froze and audio keeps going.
I can watch the same channel without issue at all with HD Homerun app.
Any idea what the deal is? I’ve been having all kind of stability issue with DVR/Live TV. I want to get an idea if upgrading tuner or antenna is going to help.

in case it matter, server Version 1.10.1.4602

I just remember more detail, I have no issue when watching via web interface. The issue only on FireTV Plex app.
I cleared cache, data, and re-installed the app. Still the same. It only pop up recently regarding freeze video and weak signal.