All the traits in the CultureTraitDefs.xml that have the TargetOrdinalConstraint property give the effect on one-too-many colonies. It appears to be the common one-off-bug.
The probable cause is that the effect counter is compared to be equal-or-less ( <= ) instead of less-than ( < ), or is initialized to zero while it should be initialized to 1.
Also see: Malevolent Ideology (Relentless) Bug post.