Hi All,
Many thanks to behickey for pointing out that Update Automatically doesn't always do what is implied and that a manual update to the latest appropriate firmware for your Sony Bravia may fix the Apple TV pixel problem - it fixed mine. Here is my story. My Sony TV is a KD-75x780f (2018 model from Costco). Step 1 - Hit HELP button on Sony remote. The existing software version appears on the upper right of the screen underneath the model number. Mine was PKG6.6555xxxx. Write that down. Step 2 - Using the internet, navigate to Sony.com. Step 3 - Choose Business & Products. Step 4 - Choose Electronics. Step 5 - Choose Consumer Electronics. Step 6 - Choose TV & Home Theater. Step 7 - Choose Smart TVs. Step 8 - Choose Product Technical Support. Step 9 - Search for KD-75x750f (obviously you would search for your model). After Step 9 I was at the KD-75x780f Model Support Page. Step 10 - navigate to the Downloads tab. Appearing on my laptop, once I hit the download tab, was a Firmware Update v6.7220. There was an option to view all applicable models for this Update and mine was among them. Step 11 - download the update file. Step 12 - follow the instructions on the download page for methods to manually install the update.
Remember the number you wrote down in Step 1? PKG6.6555xxxx (for me). The new downloaded software for my TV was PKG6.7220xxxx. Because my current software was clearly out of date I used the USB method to update my software (it is described on the download page). It was pretty simple. I copied the downloaded update from my laptop to a USB thumb drive. I plugged the USB thumb drive into the back of my TV. The TV recognized the drive and did the rest. The software update took about 20 minutes. Afterwards when I hit the HELP button on the remote the software version displayed as PKG6.7220xxxx.
Most importantly - Apple TV now works perfectly! Total time (once I knew what to do) was about an hour.