Maybe there is a hole somewhere along the inner tube that the black button can be pushed into to release the ring (bushing).

I had a Forespar pole that was similar except the plastic parts were glued on to the aluminum.
There was another plastic bushing attached to the inner end of the of the inner tube.
Both ends had to be removed to get that one apart.

As far as I know Kepmt was bought by Selden.
Might be worth a call.

Cheers,
John.