For some records (mainly on firefox, didn't get them on Chrome), I hear some small "pops" in the middle of the record, meaning there is a breakout in the audio stream.
See this audio record for example:
When I check the spectrogram of this file, there is something strange near 0.34s (the red bar):
The audio breakout becomes clearer when we zoom in at this timecode on the waveform view:
For some reason, it seems that the record just jumps/misses some audio samples...