dead spot in touchscreen vertical scroll response

Hi: for the past couple of days, my year-old z-force droid developed a “dead spot” in the middle of the touchscreen…no taps or scrolling action in that area are picked up. So for example if I scroll my text messages from bottom to top, near the midpoint of the screen the scrolling stops until my finger slides up about 1/4-1/2” past the center, then resumes. If I’m typing a text, I can’t hit “send” when the send button is in the middle of the screen above the on-screen keyboard. If I click the “hide keyboard” button the send button slides down to the bottom of the screen, where clicking on it works. The dead spot goes across the entire screen…like a stripe of dead area. The only thing I did recently was allow Android 8 to autoinstall a week ago. Rebooting in safe mode doesn’t change the behavior.