JQL - Each time I use parent != "CT-123" the filter hides something that is not in that EPIC

Question

I'm trying to setup a filter in JQL, everything works fine but as soon as I add (even if I that is the only thing I add) parent != CT-123, the filter hides another task that is not inside the epic CT-123 and is actually on a different project than the one where CT-123 is. What can it be?

Answer 1

I've resolved with the following:

(parent IS EMPTY OR parent IS NOT EMPTY AND parent != CT-123)