Plugin is redirecting other CF7 forms

I am using a number of different CF7 forms on my site, with just one using the PayPal integration plugin. The form works and redirects correctly to PayPal, however all the other forms seem to be trying to redirect to a page that doesn’t exist. When I click the submit button on one of these forms, something like “/#wpcf7-f509-o1” is added on to the end of the URL (e.g. https://domain.com/contact-us/#wpcf7-f509-o1) and displays a 404 error.

If I disable the plugin, these forms now just display the ‘Message sent successfully’ notification on submit as it should and doesn’t try to redirect.

The ‘Enable PayPal on this form’ box is unchecked on the forms that aren’t using it.

https://www.ads-software.com/plugins/contact-form-7-paypal-add-on/