Prorate Convention Populating with Incorrect Date Range

Our prorate convention dates are automatically populated at the end of the fiscal year. For both 2016 and 2017 the dates it used were very random and do not match with our fiscal year dates or asset calendar dates. We are unclear where the system is grabbing these dates. The problem we are facing is we cannot edit those dates because the prorate convention is in use. What has caused our system to start populating incorrect date ranges in the prorate convention and how can we fix this?