Go > Next/Previous Instance commands are enabled but non-functional for a selected replicant within a Smart Group.
The more general case, over here, is that the commands are enabled and non-functional for replicants inside the same group or at the root.
Group A: contains -> replicant1 & replicant2
Group B: contains -> replicant3
The commands toggle forward/backward between replicant1 and replicant3 and never to replicant2**
IOW, the “anomaly” is not limited to a Smart Group, but the Smart Group behavior you posted is consistent with the general case.
[size=85]**If the sort order is changed, the first item in the toggle sequence might change[/size]
I suspected this had a more general case; thanks for describing it.
A future release might just disable the possibility to create multiple replicants of the same item in the same group as that’s of no use anyway.