This is occurring with the 'Background image' element, rather than the 'Image' element, so there is no dropdown to select the image file. Only the file picker box appears.
If you have no site-level certificate templates, the background image will change properly when replaced in the activity instance. If you have at least one site-level certificate (even if it has not been loaded for the activity instance) then its background image will always stick, no matter how many times you try replacing the image in the activity instance using the file picker.
This is occurring with the 'Background image' element, rather than the 'Image' element, so there is no dropdown to select the image file. Only the file picker box appears.
If you have no site-level certificate templates, the background image will change properly when replaced in the activity instance. If you have at least one site-level certificate (even if it has not been loaded for the activity instance) then its background image will always stick, no matter how many times you try replacing the image in the activity instance using the file picker.
_Originally posted by @phil-r-openlms in https://github.com/mdjnelson/moodle-mod_customcert/issues/623#issuecomment-2188128562_