Are your messages a list of things or are they separate database items? If they are a list of things, it’s possible you’re running into the same problem i did:
Scroll down to where I say “So I finally solved my problem” but also possible that that answer doesn’t help you at all.
Can you share a screenshot of what you have when you click on “search for messages” in the repeating group Message settings box?
Does something like this not work?
Here are all three messages I created without any constraints:
Here is the restraint to filter by test3@email.com and test4@email.com using the "contains keyword(s)
And the results of that are as expected:
Let me know if that still isn’t it