This is what I found matching the llblgen pro project file against the old and new generated ReportingPeriodEntity.cs
You have 2 relations defined between CalendarPeriod & ReportingPeriod
ReportingPeriod refers to CalendarPeriod through the following fields:
The first relation:
CalendarID, CalendarLevelID & StartCalendarPeriodID
The second relation:
CalendarID, CalendarLevelID & EndCalendarPeriodID
In the Designer both of these relations are realised and also in both of the generated code files (OLD & NEW).
But they are switched comparing the OLD & NEW project files.
The fields mapped on relation:
CalendarPeriodEntity & CalendarPeriodEntityByCalendarIDCalendarLevelIDEndCalendarPeriodID
So in one entity class file the CalendarPeriodEntityByCalendarIDCalendarLevelIDEndCalendarPeriodID
relation is defined as the relation using the StartCalendarPeriodID
And in the other file it is defined as the relation using the EndCalendarPeriodID
So most probably the Project file was altered somewhere bewteen the old and new code generations.