Several users of Pixel 4a 5G reported that there was a problem with the phone display. It is reported that this problem began in the December update, but the January update did not include a repair patch.
Some users stated that after the December system update, there will be about a 1/3 probability that there will be no response when touching the screen (especially the navigation buttons).
The success rate of touch in the navigation bar area is very low, which is almost like the touch area of the navigation button is reduced.
The same is true after a factory reset, and also when the touch sensitivity function is enabled/disabled in the settings. Before the December update, these problems did not exist.
Google responded through a post by a community expert named David Pop. He said that Google is aware of this problem and will include a fix in the upcoming update. As mentioned above, the January update did not fix it. I hope Google can eliminate this annoying bug in the February update.
(Source)
