Mojave Mission Control Not Working Bug

Seems the Mission Control Hot Corners in Mojave is bugged. When some programs are open it works and when other programs are open it doesn't work any more.

For example, I open Firefox, Thunderbird, Itunes and all is well with Mission Control. But as soon as I open my Audible App the Mission Control in Hot Corners and keyboard no longer works. When used the Desktop screen shows up blank. Other Hot Corner settings works except Mission Control. When I kill the Audible App Mission Control works again.

Any ideas why and how to fix? Never had an issue before with the earlier Mac version.