Beware Modern Fertility ovulation strips!

I don’t know if this was just a fluke, but I bought modern fertility ovulation strips for this cycle for the first time and I completely regret spending the $15. I usually ovulate around CD 18-20 but I had gotten all the way to 25 without the slightest darkening of my test strip, I thought this was fishy so I bought another regular strip test at Walgreens and it was completely positive! Very thankful I bought the other tests on the right day! I did a sample using the same urine with the MF and the Walgreens one and only the Walgreens was positive, the other was so faint. I hope this was just us a one time thing but buyer beware!