Just looking at the new updates in 4.0.0 (looking good). I noticed however in this demo:

https://mdbootstrap.com/snippets/standard/mdbootstrap/3777139

If you place your mouse over the first of the three thumbnail images, and then quickly move your mouse over the second thumbnail image and on to the third thumbnail image, the main image area displays the second image, not the third.

If you then move the mouse off the thumbnails, and then hover the mouse back over the third thumbnail image, the correct image will display in the main image area. But if you then quickly move your mouse back over the second thumbnail back to the first thumbnail, only the second image is displayed in the main image area.

I'm guessing that while the main image is fading in/out, the mouse-over check does not work. I don't know if that is by design or by mistake.