I have seen other posts that are kind of like my issue, but not the same and none of the solutions offered have fixed the issue.
Having said that, here's what's going on:
Roku Express connected to TV over HDMI and has worked for months, just fine (until about 3 weeks ago)
When powering on, the Roku splash screen during boot display just fine, no issue
The Roku main menu loads just fine... INITIALLY... all app tiles look ok... AT FIRST
Once I got into an app (eg. Netflix) it loads but I begin to notice the display becoming blocky and as it continues to load the 'blockiness' shifts slightly (that's what i'm referring to when i say glitching)
Here's what I have tried:
shutdown and left power unplugged for a few days
switched to a different HDMI port on the TV
changed out the HDMI cable to a known good cable
installed all available Roku system updates (up to date as of 11/21/19)
What I have not tried, but plan to:
connect Roku to an entirely different TV to see if problem persists
we have multiple gaming systems connected to the same TV and none of them have any display issues, so I did not believe it was the TV... I'm just out of things to try as far as my own knowledge goes.