HTTP 405 Method Not Allowed error after clicking Button field in Page Builder

Steps:

1. Go to Content/Content structure.
2. Click Create button and select Form.
3. Create form - select Single line input and Button fields
4. Publish form.
5. From published form go to Page/site
6. Fill line input and click Button.

Actual result:
HTTP 405 Method Not Allowed error occurred. See attached screen.