Frederic Bernier 

Seems to be a user specific issue so I would look there:

1. User Permissions: The affected user might not have the necessary permissions to access the file on the shared drive. Verify that this user has the same level of access as other users who do not experience the problem.

2. Corrupted User Profile: The user profile on the RDS might be corrupted. Try recreating the user profile to see if this resolves the issue.

3. Network Issues: Since the file is on a shared network drive, intermittent network issues might be causing the file to appear unavailable. Checking the network stability and the connection to the shared drive might reveal problems.

4. Path Length Limitation: Windows has a MAX_PATH limitation which limits the file path length to 260 characters. If the path to the file exceeds this limit, it might not be accessible. Try shortening the file path or enabling long path support on the server.

5. File Locking Issues: If the file is locked by another process, it could lead to this error. Ensure that no other processes are using the file when the affected user attempts to access it.

6. Antivirus or Security Software: Sometimes, security software can interfere with the access to files on network drives. Check any installed antivirus or security software for false positives or overzealous protection settings.

7. File Corruption: The file itself might be corrupt. Since copying the file to a local drive sometimes works, try creating a new copy of the file from a version that is known to work.

8. Mapping Drive: Try mapping the network location to a drive letter as this can simplify path handling.

All guesses to be honest!