Unfortunately, this is a Gmail issue that is not under our control. Google uses their own formula to indicate where they are going to decide to truncate the content of an email. It is a combination of line count and size measurement.
One potential solution that can help is to change your SaneBox Settings to have the emailed digest come more than once each day.
You can choose the number of digests as well as the time you would like to receive them. To make desired changes, visit the Email Notifications section of your SaneBox Dashboard on our site.