There can be cases where the captured CSS (Cascading Style Sheets) URL’s are no longer accessible due to expired cache or a change in filename at a later stage. This results in heatmaps and session recordings not rendering correctly due to the missing CSS content.
To resolve this problem Matomo tries to save CSS in the database and load the same from DB when viewing heatmaps or session recordings. To disable fetching of CSS content from DB you can update your configuration file located at config/config.ini.php with the below code.
Ideally you would disable this setting only when you want to fetch the CSS content from the URL specified.
Note: By disabling this feature you need to ensure that the link is always accessible and data remains consistent.
[HeatmapSessionRecording] load_css_from_db = 0