I am no expert but do grow sans.I have a few questions. Are you using a very light soil mix with no peat?
Where do you grow this sans?
Are the rot places soft to the touch?
Have you unpotted this plant and looked at the rhizome?
Worse senerio: If the rhizome is soft, probably too much water. Sans do not need much water at all. Pitch the plant.
Hopeful:If the rhizome is hard, remove all dirt and soft spots, wash well,dry, let the rhizome dry out for a week.If the plant is rotted all the way to the rhizome, cut off the plant.
Repot: I use 1 part perlite, 1 part vermiculate, 2 parts ground bark, and mix Osmacote into the mix. The pot should have very good drainage--I use pea graves in the bottom of the pot. This works for me in south Louisiana because we have such a hot and humid envitonment. It allows the soil to drain completely and dry out very dry between waterings.Cylindrica needs very bright indirect light, protection from a rainy environment, and high temps.
Since your plant is already damaged, cut off the rotted areas until you see healthy tissue. Treat cuts with a fungicide. Put in med shade for a week to recover from shock. Then move to brighter, indirect light.
Goal--To allow this damaged plant to bloom, then put out pups, which you can raise and shape perfectly as it grows.
If this is not just too much watering, and actually a disease, do a search for diseases and treatments of sansevieria.
Johanna

the reputable garden center had it growing in a bark with perlite type soilless mixture (i cant see peat). it needed to be repotted when i got it and i havent done so yet, so it dries out very fast. the rot is soft to the touch, spreads when squeezed and has a brown fluid coming out of some of them. the rhizome looks fine. i grow it outside... but moved it into a bit of shade in order to ease the transition inside (i moved it when it was bone dry) i think the scarred over lesion was there when i bought the plant. now there are more active lesions. if the lesions are just going to scar up, i am against cutting, but ill cut it if it will die if i dont.

First, I would try to exchange this plant for another. I think there are too many rot places for this to be isolated.
If you are in the USA, we could trade. I have a few nice sized, actively growing cylindrica cv patula offsets. What else do you have?
I went to Lowes this am and found sans Grey Lady! A huge pot. What a surprise!
Johanna

thank you for the generosity and and advice, but im located in canada .

Joanna, the only way to kill a S. cylindrica is too much water and not good drainage. They will not flower if not mature. I mean that the roots have grown tight into the pot. They will not flower twice on the same leaf cluster. Do not use any soil mix with leaf mold in it. This plant grows out in Africa often in direct sun. Maybe under a tree or bush, and may go for 6 mo or more without water, and then only a few inches that year, S. cylindrica has thick rhizomes like the Iris tubers as an example. Norma

I don't think underwatering could cause these types of spots, but S. cylindrica can be killed with too little water. For the first few monthes I had mine, I underwatered it because of bad advise. It was on it's last leg. At that point I figured I had nothing to loose by watering it more. I started watering it really well once a week. I had good soil drainage, so the soil would almost dry out between waterings. Now all my Sans are doing very very well and growing like crazy. Good drainage is critical. Withholding water for long periods of time, in my opinion, is not a substitute for good drainage.