When I unlock my screen, there's a chance I'll get a black screen with a mouse cursor. The cursor changes status as though it's going over different UI elements. Though I can't interact with anything. The chance of this black screen issue happening is high under I/O intensity, and less under idle conditions. The most likely time frame for the issue happening is the screen being locked for 1/2 - 1 hour.

When successfully unlocking the screen, I notice a brief moment where the screen is black with the cursor before going back to normal. I suspect this is a security feature of XFCE to work around Xorg security issues. I also suspect under intense system use, the removal of this black screen irrecoverably times out, which is why it's far less likely to cause an issue under idle conditions.

I'm stuck for the moment as to how to solve this issue. My theory could be totally wrong. I can't find any reports on the internet that exactly match my issue.