TL;DR The apartment was robbed during our stay and the police warned us the area is becoming notorious for crime, especially against tourists

Unfortunately, the apartment was broken in to during our stay and we had many belongings stolen, despite the apartment being in a gated complex and being extra careful with locking up behind us. The apartment windows open directly on to the street as it is a ground floor apartment, so we had to keep those locked with the shutters closed for privacy. The police suspected the robbery occurred by someone within in the complex, as they would have had to have visibility of our comings and goings and had to be aware we were going to be out for a while, as they had time to deep dive through our belongings and put everything back where they found it. They also warned us that there has been an increase in crime in this area of Lisbon, especially in thefts targeting tourists.
The hosts themselves couldn't really do anything to help, and couldn't even give us a non-emergency number to report the crime. The most local police station to this apartment didn't really have anyone that could speak English, so if you are in a similar situation I would recommend calling 112 or the tourist police station and they will help you out.
I wouldn't recommend it, there are many beautiful areas of the city and plenty of other AirBnBs -but if you do choose to stay here, the apartment itself was fine, it has very little in the way of amenities. The complex has a pool which was nice but the area is pretty sketchy so be extra careful with your belongings.