Audio problems are usually caused by one of three issues:
Your audio may be clipping, which is what happens when your signal is overdriving the BoxCaster's input. Try turning down the level of the audio being sent to the BoxCaster.
Your audio bitrate may be set too low. If the BoxCaster has detected a very low bandwidth, or if you have chosen a very low audio bitrate, the audio may be "tinny". Try choosing a higher audio bitrate in the Advanced Configuration menu on the scheduling page for the event.
If the first two options do not work, you may be experiencing packet loss due to a slow network connection or another networking problem. Go into Advanced Configurations and lower your video bitrate.
Another option you may want to try is to bring your audio from a different source (e.g. from your audio mixer instead of from your camera). You can use the Red/White RCA jacks for audio while still bringing video in via HDMI. Simply go to Event Details - Advanced - Audio Source - Analog Only- Save Changes. Doing this will force the box to recognize audio into the RCA jacks only.
Reference levels for analog inputs:
Line-level, unbalanced, and tuned to a 1V peak at 0 dBu.
static, hot, distortion, distorted