It sounds like you may have auto-unlock enabled. Auto-unlock relies on your phone's GPS, but if your device or location is particular susceptible to GPS drift, your device may be inadvertently triggering the geofence and therefore the auto-unlock function. You can check out this post for more information.
To reduce the likelihood of GPS drift, we recommend keeping Wi-Fi enabled on your phone as it will reduce the chance of GPS drift. Unfortunately there isn't anything we can do app-side to prevent this from happening because the app uses the GPS location reported by your device, so if your device reports the wrong location due to GPS drift, auto-unlock will trigger. If this continues to happen you may need to disable auto-unlock for your Sesame to prevent it from unlocking when not intended. We apologize for the inconvenience!
We do have some improvements for auto-unlock planned in the future so stay tuned for updates. - CANDY HOUSE