Phone echos very badly after repair

I can’t remember if this started before or after the screen repair I performed, but it was around that time. If I’m on speakerphone or a video chat, the other parties can hear a bad echo. Sometimes it just sounds “laggy”. Some of the troubleshooting steps I have taken include:

Factory reset

Replace charge port (has a microphone on it)

Replace loudspeaker

I have no idea what else to try. I repair phones daily and have never encountered something like this. Any and all solutions welcome. Thank you!