The Split Sections by Cohort feature will add a CAR Stop Date that precedes a Start Date for classes with a future term. For example, splitting sections for Spring sections that have not started. Also, Class Calendars are not being added to newly split sections in a non-Flex school.
Programming is working on a fix to be released as soon as possible.
A fix for this issue was released in the 12/22/2020 hotfix.