For the current website I am building I have made a contact form via the Form Builder in Joomla 4.3.3 and SP Page Builder 4.0.10 although I am having the same issues in the current version 5.0.8.
The form itself works and is able to send out emails by itself. I have now however added a navigation bar using Joomla Site Modules and within that I have used SP Page Builder and the custom code(RAW HTML) block. I have done the same for the footer of the page with the exception that in the footer I am not only using custom code but also the divider and text blocks. The navigation bar and footer are displayed on all pages.
Once I added the navigation bar and footer the form I built will simply spin the sending animation without actually sending anything. Unpublishing the navbar and footer resolves the problem again. This is irrelevant of using PHPMail or SMTP. I have already looked through the forums but could not find anything useful besides someone saying to disable the modules (https://www.joomshaper.com/forum/question/1935). This however is not an option as I need both of the modules on every page.