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.
Sorry, I just realized I'm posting this in the X8 forum when I should be in the 2018 forum. I'll re-post there.