We've all been awaiting Android 11 eagerly, but now that it's there, a subset of Pixel 4a users doesn't have the experience they were hoping for. Some people have taken to Google's and XDA Developers' forums, complaining about touchscreen sensitivity problems such as unresponsive scrolling and phantom touches.
While the touchscreen woes don't affect everyone, the problem is most pronounced for those using screen protectors. Those who experience the issues found only two solutions: Downgrading to Android 10 or removing their screen protectors. The usual troubleshooting methods like rebooting, safe mode, or a factory reset don't seem to help. Someone managed to get better results by switching the Touch and hold delay in accessibility settings to "short," but only taking off the screen protector made the problems go away completely for them.
Some people speculate that the problem may be related to a new toggle that's only available on the Pixel 4: Last year's Google flagship has received a touchscreen sensitivity toggle that's supposed to make it work better with screen protectors. It's possible that Google also changed the touchscreen sensitivity on the Pixel 4a without including a toggle.
In a post on the Google Issue Tracker, a Google employee writes that the company currently views the touchscreen woes as a product issue, not a developer problem — i.e., Google currently thinks it's related to hardware rather than software. However, with the troubleshooting steps in mind, it's more than likely that it's in fact a problem with Android 11 rather than with Pixel 4a hardware. Let's hope that Google will soon acknowledge as much and push a fix. In the meantime, you should refrain from updating to Android 11 if you use a screen protector.