Could be a fungal infection. Succulents are fairly good at sealing off fungal infections if they are minor--you end up with a dried up black spot like that. Watch the humidity in the air--cut back water when it is hot and humid. Make sure succulent plants get plenty of light, and watch for scale insects and mealy bugs which can damage or kill plants.

Because the forum addresses more than just diseases. It also addresses cultural conditions and fertilizing/watering issues that can affect healthy plant growth as well as insect and other pest problems. Many times hobby gardeners are just not aware of what precisely is affecting their plants - they just know it is not doing well and assume it is 'sick'. But 'sick' can infer a lot wider range of plant problems than just diseases. So they visit the Garden Clinic forum with an assortment of ailments for evaluation and help. Sometimes it is a disease issue but many times it is something else. Diseases and plant pathogens are often tricky for even very experienced horticulturists to diagnose accurately. Very few garden clinics focus solely on diseases. The Garden Clinic forum subheading says this: "The garden clinic allows users to share information on pests and diseases."

Obviously you can reject my answer if you wish but I stand by it. I've been growing and reading about growing for many decades too and I have seen this phenomenon. What you see in your images is the callus formation which is part of the indirect organogenesis process. As to the mush there's nothing to say there can't be some rot as well as the incipient roots. Perhaps if it ever happens again you could keep the cuttings and see what happens.

Hi, I have some leaf problems with my plant. The older leaves are getting dry yellow spots, and falling off. On hte underside the leaf has a bronze colour. Seems like it's a residue on the leaf, but it doesn't come off. See attached images. Any idea what it is, and what can I do?