Step to reproduce the bug:

1. Start group call
2. Mute microphone
2. Disconnect the internet connection and wait for message «Hold on while we try to get the call back.»
3. Connect internet back
4. Wait while call reestablish automaticly
5. Participant will hear you even though microphone icon look mute.

I tested this on version 5.5.0.124 and BETA 5.7.0.123 and both was affected.
https://jira.skype.com/browse/SCW-3328