This issue is similar to UE-84380. But I tested the shelve 10164190 mentioned in the comments. It didn't work.
Similar to UE-84380 but different.
Result: Nothing shows up
Expected: "Hello" printed in red
Note: If we double click Test_02a and open it for once. The print works. But the magic loses its potency after we restart the editor.
If we unbound the trigger event and rebind it to the function again. It's fixed permanently.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-84852 in the post.