UPDATE MAY 17, 2021: A hotfix is available for DLP 15.7 MP2 that addresses these issues. See this advisory for details. A fix for these issues is being developed for DLP 15.8. A fix for these issues will not be available for DLP 15.5. 

ISSUES: When using Microsoft Edge version 90, if a user uploads a folder with sensitive data, Data Loss Prevention is unable to detect the folder upload. Additionally, when drag-and-drop functionality is used, Unknown URLs are indicated in incident reports.

The issue applies to all Data Loss Prevention versions that support Edge.

WORKAROUND: To address the described issues, disable the startup boost feature of Edge Chromium. You can disable the feature by modifying the Registry through endpoint management tools (such as Microsoft SCCM software); or by using Active Directory GPO policies. 

The following links to articles provide details about how to disable the startup boost feature: 

Registry-based solution 

Active Directory GPO policies-based solution