Emerald: Graphics problem with all themes

Hi, I just installed emerald 0.8.16-3 in Debian buster. But I have a problem with all window decorations:

When I start Emerald via fusion-icon, it looks all right for a few seconds. But after switching between two or more windows several times, it looks like this:

Everything else works fine. I'm using the open source AMD-graphics driver... When I change anything in theme settings the problem goes away, but only until I switch between windows again...