Sudden v. late ovulation?

[Girlfolk]

Hi all, hoping someone can shed some light or share their experience if anyone has been through similar.
I'm in my 8th TTC cycle (Having conceived on 3 occasions in the past and I have one living child) and my cycle has always been very regular, ovulating day 19-21 and cycle length 30-31 days. I test LH every month and use Flo app to track.
All of a sudden this month I didn't ovulate when I was due to, I carried on doing LH strips until cycle day 25 then gave up. Suddenly day 30 I had EWCM so did an LH test and it was positive. So likely ovulation day 31. so currently in my luteal phase which tends to last 10 days for me. Also I did do a pregnancy test CD 30 to rule that out and it was negative.
Has anyone else had a wildly random late ovulation then returned to normal the next cycle? Does anyone know why this could have been?

Thanks :)

@Girlfolk I think I may ovulate later than normal this month. I normally ovulate cd10/11. Have had some ovulation type pain for a few days but no positive opk and I'm now cd15. I stopped taking Pregnacare and increased my Metformin for pcos and started some lifestyle changes this cycle so not sure if thats made a difference. Weirdly my boobs are still almost swollen like pre/period! 🤔 Have you changed anything this cycle? Diet, exercise, stress?