Error - No. Series while posting in different months.

Hallo;

I have a problem with posting lines in Bank Report Journal. The lines are as follows:

Line No.Posting DateDocument No. 

1000014-03-30WBPLN14/03/001

2000014-03-30WBPLN14/03/001

3000014-04-04WBPLN14/04/001

while the other data is typical (the problem arises no matter of this).

The No. Series fot this Journal is set:

Starting DateStarting No.

14-03-01WBPLN14/03/001

14-04-01WBPLN14/04/001

But I receive the following error message:

Document No. must be WBPLN14/03/002 in Gen. Journal Line Journal Template Name='BANK',Journal Batch Name='BANK_PLN',Line No.='30000'.

What causes this error? The posting date is set to next month, so why Nav doesn't swith Series No. to another?

The debugger stop here, in Cu 13:

while the values are:

We use Nav 4.0, Polish version.