New Post: Issue with WriteableBitmapEx.Blit API

We are using WriteableBitmapEx library (version - 1.5.0).
From this library, Blit API is used to merge source writeablebitmap to the destination writeablebitmap destination.
This Blit() API is taking 60-100 seconds to execute, which is resulting very slow performance.

Code snippet for reference :
Rect srcRect = new Rect(0, 0, bitmap.PixelWidth, bitmap.PixelHeight);
Rect destRect = new Rect((frame.PixelWidth - bitmap.PixelWidth) / 2, (frame.PixelHeight - bitmap.PixelHeight) / 2, bitmap.PixelWidth, bitmap.PixelHeight);
frame.Blit(destRect, bitmap, srcRect, Windows.UI.Xaml.Media.Imaging.WriteableBitmapExtensions.BlendMode.Mask); //where frame and bitmap is writeablebitmap object.

Observations:
Issue is observed on Phone only.
If we run the app in debug mode, API takes around 5 seconds.
If we run the app in release mode, API takes around 60 to 100 seconds. Sometime more than this.

Expectations:
We are expecting your suggestions on this for an alternate solution or any modifications to be made to correct this API work.