No screen time on one day of the week

I have screen time limits set on an Xbox 1 for 8 hours per day, 7 days a week. For some reason, it occasionally sets one of the days of the week to 0 hours so I cannot use the Xbox, despite nothing being changed on the app. The day on which it selects this is random in that I will set e.g. Tuesday back to 8h because it was broken, and a few days later a new day e.g Sunday will then be set to 0h.

What is going on here and how can it be fixed?

:)