Memory Is Not Getting Released after Saving a PowerPoint Presentation in C#

In below code I am adding 30 MB image in 4 slides each.
Initial memory(Working Set) for this application is 30 MB.
After running below code and even after calling GC.Collect(), this process holds 170 - 200 MB memory. So my question is why the complete memory not being released?

Here is the link for image file: https://file.io/PqBbW7AnEuW1
This issue is reproducible with any type of image.

Aspose Slides Version - 21.1.0
.NET Version - 3.1.405
OS - Ubuntu 18.04

using System;
using System.Diagnostics;
using System.IO;
using System.Drawing;
using Aspose.Slides;
using Aspose.Slides.Export;
using System.Runtime;
using System.Threading;

namespace dotnet
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Process Id: " + Process.GetCurrentProcess().Id);
            logMemory();

            Console.WriteLine("Generating PPT....");
            AddImageToPPT();
            Console.WriteLine("Finished Generating PPT");

            GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
            GC.Collect();
            logMemory();
        }

        static void logMemory()
        {
            var workingSet = 0.0;
            Process proc = Process.GetCurrentProcess();
            workingSet = proc.WorkingSet64 / (1024 * 1024);
            proc.Dispose();
            Console.WriteLine("Working Set in MBs: " + workingSet);
        }

        static void AddImageToPPT()
        {
            using (Presentation pres = new Presentation())
            {
                for (var i = 1; i < 5; i++)
                {
                    Console.WriteLine("Addding Slide No: " + i);
                    FileStream fileStream = new FileStream("./img.png", FileMode.Open);
                    IPPImage img = pres.Images.AddImage(fileStream, LoadingStreamBehavior.KeepLocked);
                    pres.Slides.AddClone(pres.Slides[0]);
                    pres.Slides[i].Shapes.AddPictureFrame(ShapeType.Rectangle, 0, 0, 700, 500, img);
                    pres.Save("PPT-01.pptx", SaveFormat.Pptx);
                    logMemory();
                }
                logMemory();
            }
        }
    }
}

@cartositt,
Thank you for the problem description. I have logged the issue in our tracking system with ID SLIDESNET-42431. Our development team will investigate it. You will be notified when it is fixed.

@Andrey_Potapov
Can I please know the target date by when I can expect to hear back from development team?

@cartositt,
The issue investigation is planning now. I will inform you about the estimated time a bit later.

@cartositt,
Thank you for your patience. Our development team is considering options for memory optimization in such cases. We assume that the required fix will appear in Aspose.Slides 21.3.

The issues you have found earlier (filed as SLIDESNET-42431) have been fixed in this update.