Picture is slightly blur when I click on it

I use Mylio on a Windows PC.
I realised that when I click on a picture then it will become blur (OnMouseDown) and only after I release the mouse again (OnMouseUp) the image becomes sharp again.

These are RAW-files. Does Mylio show me the preview of the raw-files when I click on it or what is happening?

Is this a thumbnail or when image fully open?

On mousedown I would expect it might go blurry as it thinks you are moving the file somewhere

Fully open. (100% preview size)
It is enough to short click on it and it will take a short while to become sharp again.