Were the steps wet? My parents stayed active for a long time, but were always afraid of wet pavement and steps, for some reason. I think that before an actual fall, some people with more cautious brains tend to be alert to fall dangers.
Two other things: my father was active until last year, and then he fell gravely ill with an auto-immune disease that no one knew he had. I just saw him walk - his walk is very halting, he gets out of breath immediately upon walking 100ft, and his stride has shortened considerably. All bad signs, that I saw in my in-laws during their decline. My husband, who is a doctor, tells me that when the stride shortens it's the beginning of the end.
I think you should take your father's halting walk and step maneuvering seriously. There's been a significant decline there. Maybe a stroke?