Included in our October 7 Platform Update was the addition of code necessary to better identify forms when embedded in a Form Chooser widget. That code was intended to clarify which set of 'Payment Details' fields to submit in the rare situation when both forms in the Form Chooser had information entered into the fields but only one form was submitted.
Unfortunately that code change inadvertently impacted individual forms where one or both of the the following configurations was true:
Forms with either of the above were not rendering payment fields after the platform update. The code patch corrected the condition and the Payment Details were displaying on all forms as expected.