If the system property glide.ui.glide_list.start.locked is disabled, the Business Duration field does not show any data.
If there is no data stored in the field, Business Duration shows 0 sec when glide.ui.glide_list.start.locked is set to true.

1. Login a demo instance.
2. Set glide.ui.glide_list.start.locked property to false.
3. Navigate to the incident form, and personalize the Form Layout, add new business_duration/duration field.
4. View an incident record with existing log history, no data is displayed in the duration fields.

This is by design. The property glide.ui.glide_list.start.locked is set to true, as it is OOB setting in all current releases.