If the main line is backing up, it could be roots in the line.
When a cutter encounters the roots, it can catch, and the cable can start twisting very quickly. If the person operating the snake doesn't pull back quick enough on the cable, it car wrap the person up.
As a plumber, I've only operated a power snake a little bit. The last time it broke the watch on my wrist and I had the customer unwind me from the cable.
I went back to the shop, and one of the other guys, Gary showed me his thumb that he could bend back to touch his arm.
A snake had destroyed the tendon operating his thumb.
But neither of us died. It does happen though, So frankly we don't encourage homeowners to rent this type of equipment. It's like putting your head in a brush shredder if you don't know exactly what you are doing.
This is the type of tool that they let stupid men run, but OSHA would have a fit if a woman touched one. They are very dangerous.
I remember checking to see how much you got for a missing hand, $10,000
I think a hand is worth a lot more then that.
I hired one guy to work on my home, he has been a construction worker pouring concrete for one of the big hydro dams in the State of Washington. The guy next to him fell into the form as they were pouring concrete. He quickly yelled for them to stop, but was ordered to keep pouring concrete. There are some things that are very serious. The pay is good for the hazard jobs, but you will get hurt. That part is guaranteed.