I had a similar issue but not exactly the same. This may or may not help.
I messed with my tv for a few hours and narrowed down what I think was happening. TL;DR - turning the power off on the TV itself and back on fixed the issue. All power, not just turning it off on the remote to standby.
I have an LG C3 tv. I got this error on Disney+ like most. When I went to the settings for the Apple TV and check the hdmi connection it gave an error that it was unable to maintain a stable connection.
First, I switched the hdmi cords with my ps5, which also changed which hdmi port I was using from hdmi 1 to hdmi 3. It worked.
I then swapped them on the tv side again so it was attempting to use hdmi 1 port again but now with a different cable to narrow down the issue. It gave the errors again.
I tried all other ports. All worked except hdmi 1.
I then tried my ps5 on hdmi port 1 and it would turn on and recognize that it was a ps5, but stayed on a black screen. Did not work.
This narrowed it down to hdmi port 1 issue on the tv. This is where I was dumb. I powered everything off and back on. Nothing. Did a system restart on the Apple TV, nothing. I turned the tv off and left it off for a while using the remote. Nothing.
Then it dawned on me. The tv doesn’t actually turn off if you have the tv in standby setting on. Went to the front of the tv, under the bezel is the power button. Held it down about 5-10 seconds and it restarted.
Issue resolved. Both Disney and Apple TV hdmi check stopped having errors. If I had to guess it was a software issue of some sort with the tv itself. It may be triggered by the Apple TV or Disney app, but if I had to guess it happened from the tv not being completely power cycled in months.
All this to say “did you try turning it off and back on again?”
