iOS: prob with search with spotlight


I have a strange little problem with my spotlight search and OmniFocus 3:

I like to search a project or tag with spotlight for a quick access. With OF 3 spotlight doesn’t find ever project. Example:
I have „project a“ and „project b“. On my iPhone spotlight finds project a but not project b. And on my iPad spotlight finds project b but not project a.

Has anyone a idea? I really appreciate help.