Sneaking into MrBeast's Abandoned City

During MrBeast's "I Survived 7 Days In An Abandoned City" he spotted a mysterious person spying on them. This lurker was spotted on two of their drones, and they never found out who they were...

I found it weird that they never figured out who exactly this person was. Do they live there? Were they stalking them? Why has no one gone to find out?

So I travelled to the abandoned city, Kupari, in Croatia to find out if the city was as abandoned as it seemed, and find out who the lurker is...