Virtual device (via device tracker: see) turns to away seemingly on its own volition

I have an iOS device that uses a built-in Apple HomeKit automation to trigger an input boolean in Home Assistant to “on” or off" depending on if I’m home or away, and then an automation in Home Assistant that is triggered by a change in the input boolean, that uses device tracker: see to change a virtual device to home or not_home. This works most of the time - but I’m having a weird issue where it seems like the device tracker just disappears after a while and automatically sets itself to not_home after some idle period. See screenshot, where you can see that this virtual device is set to “home” 7 hours ago, but magically becomes not_home after some time.

Any thoughts on what the issue could be?