When using Aggregation Sum in a report, one may run into the error:
Syntax Error or Access Rule Violation detected by database (Unknown column 'sum_of_xxxxxxxxxx' in 'order clause')
This error may be caused because the "Aggregated Field" on the report may not be an actual field.
***Both the New UI and Classic UI***
You will need to drill down one or more times in the "Aggregation Field" until a field is selected.
Ex) SLA definition -> SLA Definition fields -> Duration