I keep getting this error : "error 2465 can't find the field '|1' referred to in your expression." in this SQL below. I can't see/find the reason.

DoCmd.RunSQL "UPDATE (tbl_klant INNER JOIN tbl_reservering INNER JOIN tbl_bill_lines ON tbl_reservering.Verblijf_id = tbl_bill_lines.Verblijf_id) " & _
            "ON tbl_klant.klant_id = tbl_reservering.klant_id INNER JOIN tbl_chambre ON tbl_reservering.Verblijf_id = tbl_chambre.Verblijf_id " & _
            "SET tbl_bill_lines.Factuur_nr = " & factuur_nr & " , tbl_bill_lines.Factuur_datum = Date() " & _
            "WHERE (((tbl_bill_lines.betaald) = False) AND ((tbl_reservering.pad) = True) AND ((tbl_klant.klant_id) = 397 ) AND ( # " & Format([vertrek], "m") & "# ) = " & mnd_nr & " ) " & _
            "AND ((tbl_reservering.fact_verstuurd) = False));"