Your memory is overloaded. You allocate a large size memory to heap. Try next type for this case:

• ReadOnlySpan<T> If you want to read memory
• Span<T> If you want modify values

That readonly ref struct type provide safe memory usage and it allocated in stack. The alternative of that it's Memory. It's readonly struct

In your code i have seen a mistake. Fix it if you copied exact code. The type initialized in using construction would be disposed after it

using MemoryStream memoryStream = new MemoryStream();
{
    currentDocument.Save(memoryStream);
    currentDocument.Close(true);
    
    memoryStream.Position = 0;
    logger.LogDebug("Position {Position} and Length {Length} CanRead {CanRead}",
    memoryStream.Position, memoryStream.Length, memoryStream.CanRead);
    
    byte[] fileData = memoryStream.ToArray();
}

I hope that will help you. Can you give more information and code about it? Remind me if i say wrong