We have a pipe that's joined with a rubber cuff that's putting out a noxious smell. We hired a plumber to replace it with something better and they just replaced it with a new rubber cuff that did nothing for the smell. What should we ask for to actually fix the problem?

Picture 1 is the original fitting, picture 2 is the repair. I covered the original fitting in plastic and the smell disappeared for a few days, plus smelling the fitting directly has the strongest odor, so I'm confident it's the problem. The cast iron pipe goes into the slab so it won't be easy to work with, but I'm sure there's some better sort of joiner than just a rubber cuff. I'm told there's a pipe that runs under the cuff, but I wasn't home during the repair so I'm not certain what's under there.

I'm happy to give as much information as you want, and I appreciate any and all responses. Thank you.