Issues with Glow dates

emily • me 38 :: DH 40 :: DS 2 :: TTC #2
Anyone having problems with Glow being off for predicted fertile window? I'm currently CD14 and on my 4th day of fertile CM. I just got a notification saying yesterday was the beginning of my fertile window (CD13) and the most important day for sex is Monday which is CD18. I usually ovulate CD14-16. CD18 would be too late for me.