It bugs me a lot that one of the best features of unity; hotcorners, are disabled by default. I use Unity Tweak Tool to activate hotcorners, with the upper left corner activating the workspace switcher and upper right corner activating expo.
The issue I have is that the hotcorners seem to randomly turn off either during a session or for new sessions.
In order to reactivate them, I have been launching Unity Tweak Tool, turning hotcorners off then on again, and the feature then works.
I notice a couple of work-arounds for older versions of Ubuntu but am unable to comment on those threads because apparently, I don't have enough rep!
Any advice on how to solve this issue please?