I kept trying to figure out why my find and replace wasn't working. I confirmed string type, no trailing or leading whitespaces from source file or in my replace file, etc. Finally I realized that the only 2 that were failing from my entire list were text that was in the middle of my source field. As a test I moved the word to the beginning of the field, then it worked. But my option is set to Any Part of Field, not case sensitive and not matching whole words.
I'm not sure why.
If you think you configured it right but it's not working as intended you could report it as a bug.