Here I go again.
I added an empty panel to the bottom of my screen, then added “application icons only” widget to the empty panel, then I started to pin applications to this KDE dock. It worked without any issue for a couple of days, and I got a new issue now. I reboot my system, and see my dock shrinked to the form of a small geometric square, If I open this square-panel settings, the panel unshrinks, but all the pinned apps disappears. What is this? Did I make some mistakes? Crying out loud about Latte Dock. 
You can in a X11 session, it was written for X session, and will segfault on Wayland.
I’m not sure what’s going on with your KDE 2nd panel though.
To use cairo-dock on wayland we shall install the following:
paru cairo-dock-core-wayland-git cairo-dock-plug-ins-wayland-git
BUT WHAT ABOUT SHRINKING KDE PANEL DOCK?
OK. My KDE dock panel was configured to fit to content.
And I saw issues. It shrinks.
I set it to custom width, and it works flawlessly so far.