If this is muting issue, it should be reproducible in MediaDevices example: publish, play, mute-unmute-mute...In this case, it seems that User1's microphone mute is not working.
If not, try to reproduce this in Conference example: join, mute-unmute-mute... If issue still cannot be reproduced, the problem can be in your code. In this case, please modify Conference example to reproduce the issue and send using this form.