Marcsgarden2350, if you can, prune away the wilting section of the plant, using a new blade on an "E-Xacto" knife or a single-edged razor blade. You might deem it necessary to do some additional pruning to restore symmetry to the plant; in which case, sterilize the tool.

You might consider what's going on with the potting medium it is in, namely, does it have a significant salt build up. Kalanchoe can handle some build up but does have it's limits. You might try 2 things, 1) flush the soil thoroughly to leach any salt buildup 2) keep the soil a little more wet than you used to do as this will help mitigate somewhat a buildup of salts in the soil and make it easier for the plant to pull water out of it. One last thing, if you can, pull the root ball out of the pot and look at the roots to see if they are white and healthy vs brown.

It is also possible you have been ove rwatering the plant and that has killed roots and the plant can no longer pull enough water up to maintain turgor.

Another source of salt accumulation is not enough leaching while watering combined with excess fertilization.

It's also possible that you aren't using enough water when it's time to give your plant a drink. I cannot tell you how many times I've looked at someone's wilting succulent plant to find out quickly that the plant was quite literally dieing from lack of sufficient water.

We tend to be so conservative about watering succulents that we lose sight of the fact that though these plants should not be watered very often, they still need a good drenching when it IS time to water. I allow my succulent plants to soak for awhile on their watering day. Only then am I confidant that water has been drawn up into each cell and that the entire soil volume has been properly saturated.

So, you've got lots of things to think about! When was the last time this large, old plant had a nice root pruning and some fresh potting medium?

IMHO ,.... its a root rot ... somehow related to the media

but we cant tell if its related to underwatering.. or overwatering ... and therein lies the problem ...

if you flush an overwatered plant.. well ... you are simply watering it more ...

if you let it dry ... under the assumption that it is oversaturated ... but it is already overly dry .. etc ...

its one of those situations where you are damned if you do.. and damned if you dont ...

how long have you had it.. has it ever been repotted????

in my z5 MI .. the long term breakdown of potting media [it losses its engineered ability to hold/flush water] .. leads to watering problems in winter ... aggravated by the forced air furnace.. and the resultant lack of ambient humidity.. for what is otherwise a tropical plant ...

in my experience.. its a goner ...

but that should not stop you from choosing the option you believe correct.. and giving it a go.. and seeing if you can rescue it ...

good luck

ken

ps: i have actually had pots where, when watered.. the water runs to the edge.. and the edge stays sodden .. rotting the root tips ... yet the center is bone dry ... so the plant is both overwatered and underwatered ... and to avoid such.. you should repot your plants in late summer early fall ... when you can still make the mess outdoors.. to get a good media to torture them thru winter.. indoors ... [and it doesnt help if it is sodden, and your furnace kicks down at night .. cold soggy is not good for the roots of a tropical plant]