Actually I did not just guess that. If I had guessed that it would have been amazing. Now you have to think about how I was able to find those two in the 400+ equations that you have there. And how you might more likely avoid problems similar to this in the future.
Developing the ability to find explanations for puzzling Mathematica behavior is extremely important for every Mathematica user. I really suggest that you try to figure out how you could have found this yourself. Then see if you can generalize that method to help you be able to find the answer to the next question you find.