When the watch has entered a building, the watch can use LBS for location which is not accurate. You can check the last GPS location to see where the watch was before entering the building.

To do this check the location on the map screen, and press the symbol to the left of the location bubble (it will be symbol of a satellite or an Ariel), it will confirm if the watch is using GPS which is very accurate or it is LBS which can be several kilometers away. If it is showing LBS, go into Track, set the LBS & Wi-Fi setting to off and press OK, this will show the history for the day only showing GPS locations.

This will show the last outdoor GPS location before the watch entered a building which confirms the watch is in that building.

Where you have any concerns, the quickest and most effective way to check on your loved one is to call them on their watch.