Replacement screen blinks only during phone calls

I just replaced the display/digitizer on my iPhone SE with the iFixit kit (IF327-011-3), and everything seems to work as it should — until I make or receive a phone call. With the phone active, the screen starts blinking on and off, and I’m unable to turn on the speaker, use the keypad or even hang up. Oh, except when I can. Sometimes the screen will stop blinking and behave normally during a call. Or not blink at all. No screen issues when using apps on cellular data. I’ve powered off and re-started a few times, but no change. Suggestions?