My wife gets frequent “phantom” notifications that there is someone at the door. I do not get the notifications but there is a corresponding live view associated with each of those notifications.
When using two mobile devices, check to see if the other is logged in as an Owner or as a Shared User. Some notification settings in the Ring app will apply to the mobile device used, thus if a setting to receive notifications was changed by one user, it might not reflect for another. Please also consider connection differences and ensure there is not a VPN enabled. I hope this helps!