NetFileEnum is being inconsistent, occasionally returns no data

Question

I am working on a C++ application that detects changes happening on a shared folder (using ReadDirectoryChangesW) and call NetFileEnum on that modified file/folder. This way, I know the possible candidates modifying file/folder.

According to NetFileEnum docs:

Returns information about some or all open files on a server, depending on the parameters specified.

However, NetFileEnum is not consistent, it does not always tell me who is currently accessing the resource. It seems to work only 50-60% of the time.

More specifically, say I modify \\172.20.30.40\myshare\file.txt (local path: C:\myshare\file.txt).
NetFileEnum is then called with the following parameters:

fStatus = NetFileEnum(L"\\\\172.20.30.40",
            (LPWSTR)szLocalPathStr.c_str(), // C:\\myshare\\file.txt
            pszUserName,                    // NULL
            dLevel,                         // 3
            (LPBYTE*)&pFile,
            dPrefMaxLen,
            &dEntriesRead,
            &dTotalEntries,
            NULL);

fStatus returns NERR_success (0). However, 40-50% of the time, dEntriesRead is 0. Is this a known issue with NetFileEnum? Is there a more consistent way to know who all are accessing a shared resource?