Problem with Undo and Object Positions

(Sorry, mistakenly posted this in the X8 forum originally)

Three simple objects (ie. 3 solid squares).

I select each of them by holding shift while clicking on them.

I drag them to a new position.

I press CTRL-Z to undo.

The three objects move back to their original position.  Great.

Apply a drop shadow to the first object (ie. small glow).

Repeat the above steps.

The first object moves to its previous position while the other two remain in the new positions.  I can continue to press CTRL-Z and move through the undo levels but those two objects never return to their original position.  My only choice to to reposition them properly again myself.

Now if I apply the drop shadow to the second object instead of the first, and I repeat the above steps, the first two objects return to their original position and third doesn't. 

Every object in the selection higher in Z-order than the object with the drop shadow gets left behind.

If objects with dropshadows are grouped, this behaviour can be a nightmare and it can require a lot of effort to fix.  This can be repeated on a new document.

I'm running Corel Photo-Paint 2018 v20.1.0.708 on Windows 7 with an NVIDIA GeForce GTX960, i5-4690, 16GB RAM.