I tested 1.6 RC4 and RC5 with an order form where I duplicated a standard product field multiple times. Each has a slightly different name, price and description for each. The fields are not required, however, when I go to preview and test the form, the duplicated fields are highlighted in red and indicate that I need to "Please enter a valid value" when I select next to go to the next page (this is a multiple page form, the fields in question are on page 2 of a 3 page form). But even when I filled out the fields with a numerical value of 1 (there is no range) they are still highlighted in red and I cannot continue. To resolve the problem, I need to delete the duplicated fields and recreate the fields separately (not duplicate it).
This originally occurred in RC4. I upgraded to RC5 and was able to recreate the issue. I created a new product field. Duplicated it. Saved. Selected Preview and tried to proceed through the form leaving the non-required duplicated fields empty and got the same "Please enter a valid value" message. Entering a valid value does not help.
I was using the latest version of Chrome on MacBook Pro running Lion OS X. The Javascript error console indicates no errors.
Tested in the latest version of Firefox as well and obtained the same results. I tried making it required, saving and then unchecking required, but no luck there. I disabled quantity, but still get prompted to enter a valid value when there is no place to enter a value.
I have been able to duplicate HTML sections without any problems.
I'm running WordPress 3.21.
