You could try adding the xrextras-pause-on-blur and xrextras-pause-on-hidden components to your a-scene:
<a-scene ... xrextras-pause-on-blur xrextras-pause-on-hidden>
You could try adding the xrextras-pause-on-blur and xrextras-pause-on-hidden components to your a-scene:
<a-scene ... xrextras-pause-on-blur xrextras-pause-on-hidden>