Component: Web Viewer
The cause behind this issue is the incorrect value set for X2YY_AFP parameter. For the customer, the value of this parameter was set to ALL. This parameter can have only ACIF, PAGE, LINE or ALL values depending on the level of transformation desired. The usage of these parameter values is stated in the embedded screenshot.
Because the report was ACIF and the customer had the X2YY_AFP parameter value set to "ALL" the report was transformed to PDF when it needn't have been. That's why setting the X2YY_AFP parameter value to "ACIF" resolved the issue.