questions about benefit program effective dates compared to job effective dates

We have run into some issues with enrolling some employees into leave plans and found that in some cases, the benefit program effective date is not aligned with the job effective date.

1^st scenario: the benefit program effective date is before the hire date.  This happens whenever someone’s hire date is changed to a later date, but their benefit program effective date is not updated.  This seems to be causing issues.  Would everyone agree that this would cause issues and have to be corrected?

2^nd scenario: the benefit program effective date matches the original hire date of the employee.  The employee was termed for a few years and then rehired at a later date so the job effective date is recent, but the benefit program effective date is not updated for rehires so it still matches the original hire date.  Could this scenario cause issues?  What do others do for rehires?  Do you add a new benefit program effective date to match the rehire?