Long time poster but name changed for this.
I have a neighbour in the flat above me with a young DC about 4 years old. I've lived here for nearly three years and the DC cries constantly. I mean really wailing and sobbing, at least every morning and every evening with at least a few episodes during the day. It goes on for so long that it sounds like they leave the DC alone to cry. This morning it's been going on for some time, wailing and sobbing inconsolably. The only other noise I hear from that DC is absolutely manic shrieking and giggling from being chased, tickled and rough housed with the dad throwing himself around chasing her (another post as my ceiling light has been damaged by this).
It's horrible to hear, I'm at home a lot as I mainly WFH and I'm a single parent with 2 DC. The parents are extremely unfriendly so there's no chance to ask them if they are OK or offer any help.
I'm maybe sensitive to the sound of kids crying as I feel very sorry for any child who cries this much. Each to their own and every child is different but at which point would you start to worry that there's more going on?