Labels are not displayed with bad consequences

I am using Fences 3.0.5.12.

On the machine, the labels are not displayed anymore, although the option to always display them is on.
I tried to restart the machine, uninstall Fences and install it again... this does not solve the issue.

As consequences:
- I cannot move the fences anymore
- I cannot rename the fences
- I cannot remove the fences (the worst as I created one for test right in the middle of my screen...).