I attempted to replicate this bug on Fedora 30 in a VM by installing dash-to-dock and enabling panel mode, but the previews do scale properly there. So strange...
In Ubuntu, you can easily replicate this bug by installing Ubuntu 19.10 in a VM and just launching Firefox, Files, and Rhythmbox. As the largest window, Firefox is put down to the bottom and clipped. At least on my system, disabling panel mode fixes the issue to where I can basically create infinite previews and see all the window titles, and re-enabling it triggers the clipping once again.
I attempted to replicate this bug on Fedora 30 in a VM by installing dash-to-dock and enabling panel mode, but the previews do scale properly there. So strange...
In Ubuntu, you can easily replicate this bug by installing Ubuntu 19.10 in a VM and just launching Firefox, Files, and Rhythmbox. As the largest window, Firefox is put down to the bottom and clipped. At least on my system, disabling panel mode fixes the issue to where I can basically create infinite previews and see all the window titles, and re-enabling it triggers the clipping once again.