Strange behavior:

Private Sub btnViewVendor_Click() 'ADD NEW VENDOR, OPENS SIDE PANEL
    Dim strVV As Long
    strVV = Worksheets("Data").Cells(11, "B").Value
                    
    Dim ventu As Range, rven As Long: Set ventu = Worksheets("Vendors").Range("VendorList")
    rven = ventu.Rows.Count
    With ventu
        Set ventu = ventu.Resize(rven, 1).Offset(1, 0): ventu.Name = "Vendor"
    End With
                    
    SpinButton1.Value = rven '####ERROR HERE####
    ListBox1.ListIndex = SpinButton1.Value - 1
    txtVendorName.Value = ListBox1.Value
End Sub
When this runs, I get a run-time 380; could not set the value property. If I place a msgbox to give me the value of "rven", it tells me 29. If I manually set "SpinButton1.Value = 29", I get no error. This code worked just fine when I tested it earlier today and now suddenly it's got issues. Any ideas?