The description preview isn't shown when the window is too narrow. I've managed to reproduce this in both Firefox and Chrome.

To reproduce:

1. Resize the window to less than 900 pixels wide.
2. From "the star menu", select "Create Task".

Actual result:
The field "Description Preview" is stuck on "Loading preview...".

Expected result:
Preview is shown.

Workaround:
Make the window wider and refresh the page.