Health app not displaying manually added steps - sometimes
iPhone X, iOS 11.2.6
When I play football I don't wear a tracker or carry my phone, but manually add steps based on an approximate steps/minute calculation
I tend to add these steps while cooling down before a post-football shower. Sometimes the steps are added to the daily total and appear on the graph. Other times, despite taking the same approach, this doesn't happen, so the day looks light of several thousand steps.
I have tried deleting and re-adding with different times, etc. But it appears that this is a random thing.
Any ideas what I might need to do? I'm enjoying tracking my steps, and not having to have a separate device to do so, but this is the sort of thing that will turn me off it and drive me to purchase something else for the purpose.
iPhone X, iOS 11.2.6