3:09:44pilltonFYI I also see the scrolling artefacts the others are reporting in my application. This morning, I tried to create a minimal example but failed. This is using a Parallels VM to run Ubuntu 18.04 without Wayland. The artefacts go away when using (setf clim:*default-server-path* '(:clx-ttf :mirroring :single)).
3:11:14pilltonThe problematic pane displays content using formatting-table followed by a number of histograms.
3:11:50pilltonThe artefacts go away when moving the window. I am not sure if that occurs for the others.