Sewer pipe trap issue possible

[micky50]

Need some advice, neighbors sewer drain keeps blocking up every few months. My wife and I have always chipped in with the other three neighbors for unclogging tho we never experience ours clogging up. Sure we had it clog up once and had it blown out with high pressure water from local plumber but nothing like what is happening with the neighbors. 4 houses share the sewer line and apparently. When we moved in 7 years ago the neighbor said that this would occur occasionally as they have dealt with over the years. My house is connected to another and the house on the other side of my connecting neighbor share this line as well. My none connecting neighbor on my side shares it as well and had to have his drain unclogged once as well. My connecting neighbor took it upon himself to have rowter router come out with camera and unclogged the drain this time. He was advised by technician that the pipe that connects to my drain box that channels waste to the next house has busted at the top of the pipe and has dropped and waste is building up and clogging the neighbors drains. I have attached pictures for you all to have a look. I can't make out what I am looking at and looking at the pictures it looks like it was taken with a potato the quality is not good. These houses were built 47 years ago and I am wondering how this has occurred. From the pictures below you can see the turn and what looks like a weld at top and a half like circle pipe below. Now to me it looks like a pipe within a pipe and if what the technician is saying is fact how did the pipe bust from the top? Ok so here is my theory and I am not looking to persuade anyone into agreeing with me but to correct or elaborate if my theory is somewhat correct or incorrect. My wife and I are the only occupants in our house, the connecting neighbor has 5 adults and one child, the neighbor on the other side who is experiencing the clogging as well has 5 adults living in theirs. My neighbor none connecting on my side is a 1 occupant household. The pipe is in the back garden and runs behind my house the 1 occupants house and my connecting neighbors extension and is next door neighbors extension. First is this pipe really broken? If so is it perhaps from extra weight of my neighbors extensions and how should I go about this? I am thinking of digging a trench in the next few weeks to see in fact if the pipe connected to my drain box is broken. Some advice would be great from professionals. Thanks to all who has taken the time to read this today and have a good weekend. Sincerely Micky50