Audio trouble on simultaneous translation channel?

[JKW251]

In one meeting there was a trouble that while listening the interpreted audio on the channel, the original audio can be heard at the same volume as the interpretation audio in all PC joining the meeting.

*Without problems the original audio should be heard at 20% volume of the interpretation audio.

Does anyone have any idea what might be the cause?
Is there any solution other than restarting the meeting?

Thank you.