Hi,
Another ways to check the stream coming from TVH server:
1. Install the Kodi to another device (PC, Android), install the TVHeadend client addon and try if the same issue appear.
2. Download the channel list as m3u playlist (browser: http://ip:9981/playlist - "TVH-IP" = IP of device where the Tvheadend server installed).
Try to open the channel with another video player (ex: VLC).
In the both case if the playback not perfect (interrupted sound or video), means the stream from TVHeadend server have errors (antenna signal quality?).