I tried this query again the next day and everything worked as expected. Every case I tested the query using "=" performed the same as "LIKE".

I originally noticed this issue due to an error on the application side, so I put in some error handling and reporting so if it happens again I will know right away and I can try to gather more information or test some other solutions. But without a way to reproduce the issue I'll mark this question as answered until I see the issue again.