Hey @Justjackie. It sounds like your video quality is fluctuating which can often be an indication of connection interference, sometimes resulting in black video clips. This can be confirmed via the RSSI reading of your device. Check out our Community post here to learn more about your RSSI and how to optimize it for the best video quality.
@Justjackie Great idea! Sometimes playing around with where it is helps a lot, and reconnecting the device to a wifi extender could help as well. If you go down the route of reconnecting it to a wifi extender, make sure you reset it up to the extender's network by going into your Device Health and selecting change wifi network.