There are two behaviors that IMHO should be corrected:

1. Edit mode inconsistency
If a task is highlighted, it can be edited by clicking on the pencil icon on the right border, or by using the space bar. However, if you double click to open the details screen, the edit pencil is on the bottom left of the window, instead of the upper right.

2. If task detail is opened by double-clicking a task, esc doesn't exit that view, it closes the entire window. The program must be re-started to see the window again!
But, when editing a task, esc has the (expected) effect of closing the editing window without saving the edit.
I propose that you make the esc key behavior consistent - close the edit/detail window only.

I hope this is helpful,

Julian