Restarting the server on the fly ignores set levels and mixes everybody at 100%

**Describe the bug**
Restarting the server sets levels to 100%

**To Reproduce**
restart a running server with clients on it and notice how it ignores the set gain levels and mixes everybody at 100%

**Expected behavior**
the server should mix everybody at the individually set levels

**Operating system**
linux, windows, macos

**Version of Jamulus**
3.6.2 and before
