Hello
STD MRP functionality explodes the requirements for each planned production order ( or batch order).
Based on your issue , it sounds like the MRP is not exploding the requirements for your formula items.
Please check the coverage group used by the MRP for your SKUs and make sure the number of days on the field explosion has a certain number of days to cover your demand.
If the settings on the field explosion is correct , check the plan you are using and make sure there is no flag ticked on the field explosion with zero value.