File redirects do not work for files with "=" in the filename. For example https://commons.wikimedia.org/wiki/File:Annals_of_the_South_African_Museum_%3D_Annale_van_die_Suid-Afrikaanse_Museum_%281898%29_%2817796645323%29.jpg has source code:
#REDIRECT [[File:Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum (1980) (17796645323).jpg]]
but it shows up in https://commons.wikimedia.org/wiki/Category:Files_with_no_machine-readable_source and other similar categories.