It was already scientifically proven in 2016 that Mammillaria geminata is the older name. And M. karwinskiana does not fit the plants that we identify today under M. karwinskiana due to various characteristics such as reddish flowers see: http://www.mammillaria.eu/Probeartikel/Probeartikel_4_2016.pdf
Mammillaria nejapensis belongs now to Mammillaria geminata see aswell Cactusworld (2020): 38(4): 315-320.
Unintended disagreements occur when a parent (B) is
thinned by swapping a child (E) to another part of the
taxonomic tree, resulting in existing IDs of the parent being interpreted
as disagreements with existing IDs of the swapped child.
Identification
ID 2 of taxon E will be an unintended disagreement with ID 1 of taxon B after the taxon swap
If thinning a parent results in more than 10 unintended disagreements, you
should split the parent after swapping the child to replace existing IDs
of the parent (B) with IDs that don't disagree.
