I had a similar experience on a 126 car with the upper radiator hose. It slid off the upper radiator pipe. Not long before this I had checked the snugness of the hose clamps.

The interior of the hose felt slick as I refitted it to the radiator pipe. I suspected age, although the exterior of the hose seemed ok.

Purchased a new OEM hose and have not had a reoccurrence.