Noisy, low-quality infrastructure, especially the bedroom ( no value for money)
The only bedroom in the house has a so thin drywall that let you listen to every conversation of your neighbor at every time of your day and night. Moreover if your neighbor moves in the apartment you could enjoy the shaking of your bedroom, because of the room infrastructure.
If you are lucky enough you could also hear the neighbor (other Airbnb guest) shouting all night till 9 am drunk and wasted.
If you are not lucky you can hear all the discussion, chat, laugh and move all day and night.
Fixing the wall issue won’t be a big cost, but the owner probably prefer to charge you a high price and not renovating. The people sleeping in the room in desperation took a hotel room looking for some rest, but according to the owner the apartment is perfect.
Oh last, but not least, watch out for the stairs handle, they are not safe and they are not properly fixed in the wall. You could easily fall down all the stairs.
I am sure I will visit Madrid again, but not in this place. I never found myself in such a situation in 15 years of travel.