additional tracks record slower

Hello. I am on a Mac OS 11.0.1, Audacity 3.1.3. I imported an mp3 file that I recorded (practice tracks for my team), and added a stereo track to record some harmonies. I’ve done this in the past. But when I go to play it back, the second track is slower and does not match the original track.

I am using a USB microphone into the mac (I also tried this with the built in mic on the computer). I am using headphones to hear the music so the only thing the mic should be picking up is the singing.

Any ideas? I made sure all other programs were shut down.

By “slower” do you mean the pitch differs, or that the tracks are not in sync?
– Bill