TL;DR
Section periods depend on dates, cycle rules, bell schedules and matching schedule tags. Check these together when a class is missing or overlaps.
Steps
Open the section in Insights and review each schedule entry.
Check its date range, cycle day, period number, teacher, room and schedule tag.
Compare the tag and period with the bell schedule applied to the affected date.
Review conflict indicators and correct the responsible rule.
Save and inspect one affected student and teacher schedule.
Do not remove a conflict simply by hiding a class. Check whether the overlap is intentional, an optional class, a special-day rule or duplicate imported data. Coordinate changes to synchronized schedules with the source system.
In Sections, use the row’s three-dot menu: Edit details for section settings, Edit schedules for periods, and Manage conflicts when available. Clicking the section name opens its overview.
Related help
Create special days and bell schedules · Resolve missing or incorrect classes · Understand school synchronization