Method Exists doesn't detect already created keys - excel

Question

I'm trying to get number of unique ids with given values on given columns. I decided to use Scripting.Dictionary for this as follow:
Public Function getSoldToIrr(umowy As Range, bi As Range, irr As Range) As Double
Set dict = CreateObject("Scripting.Dictionary")
Dim lastRow As Long
lastRow = umowy.Rows.Count
bi_with = 0
irr_with = 0
ifff = 0 'count how many new values
elseifff = 0 'count how many duplicates
For i = 1 To lastRow
If umowy(i, 1) <> "" Then
If Not dict.Exists(umowy(i, 1)) Then ' if new id
dict(umowy(i, 1)) = Array(bi(i, 1), irr(i, 1) * bi(i, 1))
bi_with = bi_with + bi(i, 1)
irr_with = irr_with + irr(i, 1) * bi(i, 1) ' if bi and irr
ifff = ifff + 1
Else ' if found duplicate id
If dict(umowy(i, 1))(1) = 1 And bi(i, 1) = 1 Then ' if duplicate already had 1 on bi and now has bi
If dict(umowy(i, 1))(2) = 0 And irr(i, 1) = 1 Then ' if duplicate had 0 on irr but now has 1
irr_with = irr_with + irr(i, 1) * bi(i, 1)
dict(umowy(i, 1))(2) = 1
End If
ElseIf dict(umowy(i, 1))(1) = 0 And bi(i, 1) = 1 Then ' if bi was 0 and now is 1
dict(umowy(i, 1)) = Array(bi(i, 1), irr(i, 1) * bi(i, 1))
bi_with = bi_with + bi(i, 1)
irr_with = irr_with + irr(i, 1) * bi(i, 1)
End If
elseifff = elseifff + 1
End If
End If
Next i
MsgBox dict.Exists(umowy(1, 1).Value) ' returns False
MsgBox dict.Exists(dict.Keys()(0)) ' returns True
MsgBox umowy(1, 1) = dict.Keys()(0) ' returns True
MsgBox dict.Count ' returns 8000
MsgBox ifff ' returns 8000
MsgBox elseifff ' returns 0
getSoldToIrr = irr_with / bi_with
End Function
umowy is my id and those values are strings like 18/07/KOR/2020, bi and irr columns are binary columns. umowy has some duplicates but for some reason my dict takes duplicates as new keys and my code does not get into Else ' if found duplicate id.
Also if I write dict.Exists(umowy(1, 1).Value) or dict.Exists(umowy(1, 1)) I get False, but dict.Exists(dict.Keys()(0)) gives me True as umowy(1, 1) = dict.Keys()(0) and umowy(1, 1).Value = dict.Keys()(0)
What can be a reason of such behaviour?