When I start I start System -> Preferences -> Appearance I see that many of the themes don’t have thumbnails and show a question mark icon instead.
As a result, mate-appearance-properties tries to generate the required thumbnails. This activity loads a single CPU core to almost 100% and never completes. Upon closing mate-appearance-properties the window is closed but the process continues to run, indefinitely in the background, occupying almost 100% of a CPU.
If I kill the process then CPU load returns to normal, but the next time mate-appearance-properties is executed a CPU core is fully utilised again.
Regards, Eber.