I looked at your code and I'm not sure why it's changing. If you want to avoid it doing that, try using the editor that's built into the Cpanel. Login to Cpanel, go to File manager, then find your form, select it and then use EDITOR or CODE EDITOR. You will need to edit the code and add the action. Here's a great reference to guide you in using formmail:
Using Formail for Contact Form
If you have any further questions, please contact technical support or leave a comment at the bottom of the page.
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