That unfortunately is a characteristic of Pivot tables. Nothing can be done, except recreate the Pivot table from scratch.
If this becomes a regular/daily problem, then it might be worth checking into VBA code to construct the Pivot when needed, which avoids this problem. And VBA code with Pivots, if designed correctly, can be quite fast.
old, slow, and confused
but at least I'm inconsistent!
You can use below code for removing old field values from pivot table
Dim wbBook As Workbook
Dim wsSheet As Worksheet
Dim ptTable As PivotTable
Dim ptField As PivotField
Dim ptItem As PivotItem
Dim i As Long
Set wbBook = ActiveWorkbook
On Error Resume Next
For i = 1 To 2
For Each wsSheet In wbBook.Worksheets
For Each ptTable In wsSheet.PivotTables
For Each ptField In ptTable.PivotFields
For Each ptItem In ptField.PivotItems