"Sticky Hose Syndrome" started with the hoses supplied with the Dual-50. Apparently Kirby's hose supplier changed the formulation of the hose at that time, because I've never seen a red 500-series hose with that problem nor the 562 or Sanitronic tan hoses. Only the tan D-50 hose, the green D-80 hose, the "milk chocolate" Classic and the "dark chocolate" ClassicΩ.
And I've never seen a red Classic III hose with this problem, so apparently the Kirby hoses were reformulated again.
I don't know what to tell you about how to remedy it. I've never found anything to remove the stickiness or reverse the stiffness.
Also, some ClassicΩ hoses also develop a coating of a white powdery substance that may be the same kind of mold that affects pink G.E. canister and the G.E. Roll-Easy attachments. The mold on the G.E. attachments can be eradicated by spraying the affected pieces with chlorine bleach then immediately rinsing it off. I've never had a ClassicΩ machine with attachments so I've never tried the bleach treatment on the hose, but I have seen a few of them over the years with that white coating.