Weird portal record creation

I have a HTML form to create a new record in DB1, with coding so a new portal record is also created. The relationship is based on an auto-entered serial number field - when the DB1 record is created, the serial number field is autoentered for both the new record and the new portal record. This was working fine. Then, I started looking into ways to verify that the portal record fields were completed on the HTML form. Due to Javascript problems (outlined in an earlier message, which no one has replied to :confused

I decided to define the validation for the portal fields in DB2 as 'required' and let FMPro return and error message if the fields were not completed. On submission, FMPro is returning an error message, and not generating a new record in DB1 until all fields are entered. HOWEVER, and this is the really weird part, a new, very incomplete record is being generated in DB2 with a serial number that would be appropriate for DB1, and the serial numbers in DB1 are 'jumping'. In other words, if I am on serial number 3, and I get two error messages before all fields are completed correctly, DB2 will create records with serial numbers 3 and 4, and DB1 will jump to create record 5, and DB2 will also create record 5.

Can anyone tell me why this is happening, and how to correct the problem?

Thanks!