Moved to web Gateway forum for better chance of answering
Are you using the SSL Scanner with Content Inspection? If so, have you tried bypassing the host or the test client IP address from the SSL Scanner? I'm not familiar with vidyo, but if they are using a proprietary protocol that is not HTTP and you are trying to decrypt that traffic then it will fail. Short of that, my recommendation would be to open a case with support and supply a feedback and the tcpdumps that show the Web Gateway is resetting the connection.