We had a clogged drain, and when the washer pumped out the water, it would backup into the bathtub in the guest bathroom. We noticed our master shower was draining slowly.
I called a plumber and he tried the vent pipe above the tub, and the clean-out in the back yard with no luck, and he was pretty sure there was a problem. He got out the video camera and scoped the pipe, and our household sewer pipe was not aligned properly with the main sewer pipe. The connection had shifted. Maybe the ground had shifted as a cause, and of course the issue was right underneath my storage building. It might have been one of the earthquakes caused by oil drilling companies waste water injection. The state agency in charge of that made the oil companies stop pumping water down in the area, and the earthquakes stopped. We never had as much as a crack in the ceiling from the earthquakes. It may well have been just the clay settling over the years after the main was installed.
We have a large Koi pond that blocks access for a backhoe to come in from the west, so they brought in a cute little backhoe that fit through a standard gate on the east side, and he was master at running it. He had to dig along the side of the sidewalk next to the clean-out, avoiding my trench where my sprinkler system main lines are, around the building and to the area where the main sewer is and he dug a very deep hole.
You can see the top of his head as he was gluing the new section of sewer pipe to the main line. The good news is the main sewer line for the neighborhood runs under my back yard, and we did not need to go into anyone else's back yard. We have pure clay for "soil" and it was dry, so he did not bother bracing the walls of the hole as he climbed in. It was like digging into pottery, just hardened clay brick.
It was expensive, but all is fine now.