ffmpeg sources out of sync

When I run this ffmpeg command, it should record two identical audio channels from my microphone to output.mkv

ffmpeg -f pulse -i default -f pulse -i default -map 0 -map 1 output.mkv

Instead the second channel is always about 1-2 seconds behind the first one. There is also a 1-2 second delay between ffmpeg outputting

Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, pulse, from 'default':
  Duration: N/A, start: 1589895393.733811, bitrate: 1536 kb/s
    Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s

and

Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, pulse, from 'default':
  Duration: N/A, start: 1589895395.008402, bitrate: 1536 kb/s
    Stream #1:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s

which might be causing the problem. How do I make sure the audio channels are synchronized when recording? I was initially recording audio from two different sources, but while troubleshooting I discovered the audio was still out of sync with two identical sources.

Sample audio file of me clapping (Open with Audacity to better see the difference.)