xfce4 using 100% cpu

[tech-lists]

Hi

context is:

12.1-stable r359156, amd64
xorg-7.7_3
xorg-server-1.20.8,1
xfce4-wm-4.14.0_1
xfce4-desktop-4.14.2
nvidia-driver-440.64

the graphics card is NVIDIA GPU GeForce GT 640 (GK107) with 2GB RAM

For some reason, xfce4 (and *only* xfce4) is always at 100% CPU.
Other window manager environments don't have this effect. For example
windowmaker. When invoking with xinit, top shows Xorg using 100%. 
So I'm unsure if it's xfce4 alone or some xorg <-> xfce4 interaction.

xinit launches xfce4 like this:

[snip]
exec ck-launch-session startxfce4
[/snip]

How can I go about fixing or even debugging this? xfce4 is otherwise smooth,
fast

thanks,
-- 
J.
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