Pale Moon 32.2.0

[Goodydino]

Since the last two versions of Pale Moon, the sanitize window sometimes opens transparent. I would like to know why this happens (only to one child window), and why it happens only sometimes. I found that I could remedy it by making something in a listcell in a listbox change when I hover on it. Sweep the cursor over the listcells to make them change and the window will become opaque. How does that work?
I have seen the same thing happen with SeaMonkey. It uses a series of checkboxes rather than a listbox, but the remedy is the same.