Adding a folder path to the file path exclusions in Microsoft 365 Endpoint DLP does not prevent Tailspin_scanner.exe from accessing protected sensitive information. Instead, it would exclude those files from DLP protection, which is not the intended outcome.
To block Tailspin_scanner.exe from accessing sensitive documents while allowing it to access other files, the correct solution is to use Microsoft Purview Endpoint Data Loss Prevention (Endpoint DLP) and add Tailspin_scanner.exe to the Restricted Apps list.
Endpoint DLP allows you to block specific applications from accessing sensitive files while keeping general access available. Restricted Apps List in Endpoint DLP ensures that Tailspin_scanner.exe cannot open, copy, or process protected documents, but it can still function normally for non-sensitive content.

Explanation:

The issue where users sometimes can upload files to cloud services and sometimes cannot suggests inconsistent enforcement of Endpoint DLP policies. This can be caused by the unallowed browsers in the Microsoft 365 Endpoint DLP settings are NOT configured. Also, there are file path exclusions in the Microsoft 365 Endpoint DLP settings.
Endpoint DLP can block uploads only when using unallowed browsers. If unallowed browsers are not configured, users might be able to bypass restrictions by switching to a different browser. This could explain why uploads sometimes work and sometimes don't, depending on which browser is used.
File path exclusions allow certain files or folders to be exempt from DLP restrictions. If a specific file location is excluded, files stored there won't trigger DLP policies, leading to inconsistent behavior. This could result in some uploads being blocked while others are allowed.

The requirement is:
You need to provide a user with the ability to view DLP alerts in the Microsoft Purview portal. The solution must use the principle of least privilege.
Step 1 - Understanding the roles
Compliance Administrator # Full access to compliance features, including creating/editing policies. This is more than needed (not least privilege).
Compliance Data Administrator # Can manage compliance features and data governance, but still more permissions than required.
Security Operator # Can view and respond to active security incidents and alerts, which is more than just viewing DLP alerts.
Security Reader # Read-only access to security-related features, including viewing DLP alerts, Microsoft Purview alerts, incidents, reports, and recommendations. This matches the requirement precisely.
Step 2 - Microsoft Documentation
Microsoft Learn states:
Security Reader role:
"Can view and investigate security events, reports, and alerts without the ability to make changes."
# Reference: Microsoft Entra built-in roles - Security Reader
Step 3 - Apply the principle of least privilege
Since the user only needs to view DLP alerts (not create or manage policies), the Security Reader role is the minimal role with sufficient permissions.