We have recently migrated from IVc3 to IVc4 and we are encountering a strange behavior with the printing of invoices.

The parameter for "Final Invoice" is not correctly set. I have had my users save their defaults and I have made sure the default at the form level is set to "YES".

I am being told that this flag is somehow being switched to "NO" and my users are printing proforma invoices because they are not used to checking the parameters.

Has anyone else encountered this problem? What is the fix?

I'm not sure if this is your problem, but checking the script it seems like there is 1 place that the script will change it back to 'no' on you, in Fix 1363442:

|* Flag 'Final Invoice' not set to 'No' when returning from form 2. (DF
|* 215363)

So, it seems that if the 'printed' flag is set to 'yes', and you are on form 2, it will jump to form 1 and set both printed and definite to 'no'.

Not sure what would cause you to be on form 2 with the 'printed' flag set to yes, but it would cause the problem you describe.