Hello! My mom, received a Thanksgiving Cactus last season and it has been doing pretty well for most of the year. She said that in the last few weeks however, arms of the cactus started falling off. Unfortunately, I don't have any experience with this plant, and after doing some research on the internet, I still wasn't sure what the issue is and didn't want to give bad advice. About two month ago she repotted it from the nursery pot it came in into the glazed ceramic pot in the picture. I warned her that in the bigger pot it would be easier to overwater it, so she says she has been very careful to water it only a little and only every other week or so. She is fairly forgetful about watering though, so she admitted than it might have been less often than that. When I was over last night I stuck my finger down as far as I could make it and it was dry all the way down. This inclines me to believe that she's not over watering it. In addition, the discolored base was dry and hard not squishy like I'd expect from root rot. Has anyone had this experience before and know what the issue might be?

Something has caused the roots to shrivel up. Either from rotting, which sounds unlikely from the described watering, or from lack of water.

If you cut off the brown part of the stem in your hand and lay what is left of the green part on the soil surface, it's likely to take root if there is some moisture. The roots come from the spot where the sections connect.