Thanks for the answer Octavia!
My pipeline has only one action. So it affects the whole execution since it never terminates.
Being more specific:
I have a pipeline that has 1 action. Executing SSH commands. I'm actually executing a git pull on my server. It does not have any merge conflicts or anything in particular that could provoke this.
The pull is done correctly and I can see my changes live. The problem is that it remains in 0% of execution, I thought it would timeout eventually but it actually remained like that for a whole night until I decided to cancel the execution of it manually.
It would be nice to force the execution of the pipeline after I do my git command.