The echo occurs when the sound of a video played within Explain Everything is captured by the device’s microphone during recording. This generally happens when playing a video within the app and simultaneously recording.
To avoid this issue, you might try these approaches:
Use headphones. By using headphones you prevent your microphone from picking up any playback audio. You could also turn your device’s volume all the way down if you don’t need to hear the audio from an inserted video object.
You can use the Microphone Mute button to manually control when the device’s microphone is muted. To enable the Mute Microphone button, please go to Record tab in your Settings (gear icon in your Profile page).