"Form of Payment" comes up empty when editing the submission in the submissions page.

While doing this example I also noticed that the "form of payment" field also comes up empty, this is not good because the original info is being changed even if I don´t touch it. Is this supposed to happen?

I cloned your form and made a test submission. It appears that I was not able to replicate the issue with the "Form of payment" field.

As seen at the end of the gif, the "Form of payment" still has "Wire Transfer" selected when I edit the submission. Please try clearing your browser cache to see if that fixes the issue. Here's how: How to Clear your Form Cache

If you need further assistance, do let us know.
Regards.