Hey @Competo
Yup the scheduled flow in Power Automate is random at times, it will not run exactly at 1pm, it will run 12:59 or 1:00.
In my case it always ran after 1:00, like at 1:01, 1:02. Not sure in your case how its running before the time.
In my case I was using Run weekly. And I find this better that running a flow hourly.
In that you can select days you want to run, select hours and minutes at exactly when to run. If you set to 1:00, it wont run exactly but around 1:01. So be careful.
Difference between hourly and weekly:

You will have to select 0 in minutes to run it near to 1 pm. Otherwise it will run randomly.

I hope this helps 🙂