Is FF always accurate with ovulation?

Danielle

I feel like my temps were a little off some days. Room is warmer/colder some nights. I had a positive LH strip on July 18th. Really thought ovulation was that night or the next day and FF is saying the 20th. Wonder if I didn’t BD enough now. And the 18th was a night he really exploded (sorry for the tmi). I thought I was 5dpo and my cross lines appeared today saying 3dpo.