In Flexera scope version 5.1.17 and 5.1.2, ServiceNowToFNMS script includes used Glide Aggregate to get the total record count which uses the chooseWindow() method to get the record counts.

As per the latest ServiceNow Documentation Product Documentation | ServiceNow chooseWindow() method is only supported by Glide records so if we fetch the total record count with Glide Record, we get a correct output but not with Glide Aggregate.

Solution:

1. Go to Script Include -> ServiceNowToFNMS
2. Within the script look for the function name: sendData
3. Look for the following line of code:

// agg.chooseWindow(recordFrom, recordTo);
//        agg.query();

var totalRecords = viewRec.getRowCount();
// agg.query();
// if (agg.next()){
// totalRecords = agg.getAggregate('COUNT');
// }
​

Copy over the code (Or comment out lines 82-83 and 86-89, then remove comments for line 85

4. Save/Update

Outcome: 

x_fls_flexera_fnms_asset XML file is generated completely and the export job is marked as success

More information: 
Link for reference: https://docs.servicenow.com/search?q=chooseWindow