The EMS drops the connection as soon as the "Unable to read value" error is detected. The FMLE and VLC may tolerate this type of error, but the EMS adheres to the RTMP and AMF specifications strictly. This is to prevent clients subscribing to the stream from detecting the metadata error too late.
Perhaps the manufacturer of Avercaster Duo can provide you an update to fix this bug?
Cheers,
Don