The table of media transcodes on the File: detail page only shows items listed in the transcodes table -- this means that anything that got deleted/missing due to an error (eg T100211) or never got defined due to addition of a new transcode definition cannot be reset cleanly.
(We used to auto-readd queues on-demand when a video got used in a page rendering, but this was super expensive when adding stuff.)
Might be nice to fill out the table with expected-but-missing items and provide a reset button to force them to generate.