If trying to change the picture inside a feature box in the front editing tool, the page is broken. This can be tested on the front page.
I have got this problem before on different addons. I have been told to rename files inside the sppagebuilder/addons that reside in the template folder. But this seems not to work any longer. In this case, I have tried to rename the site.php in the sppagebuilder/addons/feature because because the problem is the feature box.
For now I have rolled back with Akeeba to a state where problems is limited to the start page.
If I go on with updating sppagebuilder from 8.8.0 to the latest 3.8.3, more problems show up. The component event manager do not show up any dates on the course event list.
I have tried different updatings by rolling back and then updating the Joomla platform and its components but without success.
This is how the problems mostly came. It is after an update of the sppagebuilder or something else in the layout system.