500 internal server error upon form submit from landing page

Your software
My Mautic version is: v3.1.2
My PHP version is: 7.3
My Database type and version is:

Your problem
My problem is:
I designed a survey on Mautic landing page. Upon pressing submit the button keeps loading and stalls. I keep getting a 500 internal error unless I am logged in. What could be the cause? this did not happen before and just started randomly.
Please help.

You added a content maybe that is not welcome? Scripts maybe?