Validation message in webform

CentOS 8.2
mautic 3.1.1-rc (from github)
php 7.3.22

Your problem
the validation error message of a webform is put in the url when hitting the submit button, so I will land on a 404 page. Is that supposed to work like that?

?mauticError=Errors%3A<br %2F><ol><li>Bitte trage deine E-Mail ein<%2Fli><li>Die Nachricht enthält keinen Text.<%2Fli><%2Fol>#contact_fo

How can I get the error message (e.g.: Enter E-Mail or Enter Name) actually show up near the form when the field is required and not filled out?