I recently discovered a bug in Facebook's link-sharing feature. Since fbclid is added to shared links as a URL parameter, users started encountering 404 errors. The reason for this is, the fbclid parameter is only used on Facebook, and does not actually exist on the target site.
I have a strict policy of not allowing non-existent URL parameters, since these can lead to duplicated content with search engines, as well as occasional on-site issues. All known parameters are kept in a list, and if a used parameter is not recognized, a 404 error is instead shown to the user.
Facebook recently changed their link-sharing feature to include the fbclid parameter, which was breaking link-sharing of content from Beamtic.
The problem should now be fixed.
Currently the parameter is allowed, but in the future I might 301 redirect malformed URLs to ensure compatibility with other software.