@LiamR89
Please consider changing your Formula to the following:
Filter(
ForAll(Sequence(DateDiff(dte_Event_StartDate.SelectedDate, dte_Event_EndDate.SelectedDate, Days) + 1),
With({_cDate: DateAdd(dte_Event_StartDate.SelectedDate, Value, Days)},
{
AddedDate: If(WeekDay(_cDate) = 7 || WeekDay(_cDate) = 1 || !(_cDate in NonWorkingDays.Date), Blank(), _cDate)
}
)
),
!IsBlank(AddedDate)
)
That should give you what you are looking for and perhaps a little easier to maintain and change.
I hope this is helpful for you.