Firefox sharing mic intermittently stops sharing

I play online bridge (Trickster) twice a week and set up Firefox to share video and sound with my USB mic. (Windows 10 desktop, Trickster opened in Firefox). Most of the time it works fine but occasionally the other bridge players will tell me they can no longer hear me. When I click on the mic icon the message is that Firefox is using the mic. The settings still say that the mic is being shared. Sometimes a windows reset will fix the problem but not always. Can you explain what might be happening.