Ovulation Prediction

Has anyone experienced Glow predicting their ovulation wrong ? We've been TTC for years. Drs say nothing is wrong with either of us . I'm starting to wonder if maybe glow isn't giving me the right ovulation prediction? Most times , my CM is not a raw eggwhite consistency during what is suppose to be my ovulation period by Glow's prediction, & me logging my symptoms never seems to change the prediction. I know I can buy tests , & that is my next step. But I'm curious to know if anyone else has experienced this.