Hi!
In which version of Acumatica were you able to edit the Last Generated date? If you were able to edit this field, it was a bug.
Once a generation has been done from a service contract schedule, it cannot be reverted. If there is a mistake on the appointments or service orders generated, the changes should be made on the appointments or service orders. It’s possible to make mass edit if a GI is modified to allow mass updates.
If changes are made in the schedule, these changes will affect the next docuement generation.
What kind of edits were often made on the service contracts? To help us understand the business nedd and maybe we can improve how it works.