I have tried this as i was experiencing the same problem .... however i have sorted it and it does work on my updated Kemper stage
select a rig ..... ie, performance 1 slot 5 press and hold rig button ...it will then give option to copy rig ! then select another performance and slot i.e.. performance 2 slot 3 ...press and hold rig button paste will then come up as an option on top soft button simply paste it it works i have just done it .