Partial data imported as part of Discovery imports

Issue Summary

Importing a Discovery zip file does not import all the data into Insight.

Steps to Reproduce

1. Upload a discovery zip file with multiple xml files with different start dates
2. Import data

Expected Results

Complete import of all the data from the zip file

Actual Results

Partial data(data from the files that belong to the oldest date in the zip file) is imported

Workaround

Ensure the zip has XML files starting around the same date