My Polaris 280 stays in the pool 24/7. Have had it for 10+ years. The bottom part had a hole due to wear but the plastic has done well. Maybe your cleaner has been sitting on the deck (out of the pool) in direct sunlight. You can buy replacement parts or a refurbishment kit (mainly tires, bearings and turbine) if you wish to maintain it. Also, pool stores sometimes have sales i.e. Polaris Cleaner weekend event or something similar if you wish to replace it. Alternatively is a robot cleaner.
If it is just the hose, that may be more susceptible to UV rays - especially the part with the floats on it. The tail hose has wear rings (there are either blue or white) they are supposed to wear over time and be replaced. They keep the tail hose off of the pool bottom. If not, then that tail hose will rub on the pool and create a hole in the tail hose.
Maybe post a picture of the parts that are crumbling.