Connecting to shared network resources doesn't always work

I am working with the code from this tutorial to access files remotely C# NetworkConnection for file share or other remote communication

I can connect to the remote directory and access the files which are just .jpg images.

This is the code for accessing the images:

[HttpGet]
public ActionResult GetPhoto(string cpuNr, Int64 imageNameNr)
{
    string source = @"ipadress\photos";
    string imgPath = Path.Combine(path where the image is from the cpuNr and imageNameNr build toghether);

    FileContentResult result = null;

    using(var share = new NetworkConnection(source, new NetworkCredentials())
    {
        byte[] fileContent = System.IO.File.ReadAllBytes(imgPath);
        result = File(fileContent, "image/jpeg");
    }

    return result;
}

This works fine in most of the cases. But sometimes I get an error:

Network Error: System.ComponentModel.Win32Exception (0x80004005):
Error connecting to remote share.

The source couldn't be accessed. It doesn't mean that a specific image can't be always accessed, because sometimes it does and sometimes it doesn't.

Is there any way around this error, any fix, because I can't find anything that will help me further for finding the reason of this problem or a solution for it.

EDIT The same file, from the same path, with the same user, sometimes gets accessed normally, but sometimes not.