Trying to make a media player, media server, all by using ffmpeg and a pre-built media streaming engine as it's core. Python and SQLite. About a week's worth of effort every time until it begins to go too far off the rails to be reliable to continue to develop with. It never did get the ffmpeg commands right, I had to go back to crafting those by hand, it never did get the streaming engine to play in the browser's video player in the supported hls and dash formats. Asked it to build a file and file metadata caching layer and then had to continue to re-prompt it to poll the caching layers before trying to get values from the database. Never even got to the library, metadata, or library image functionality. Had to ask it to create the rbac permissions model I wanted despite it being very junior-level common sense (super-admin, user-admin, metadata admin, image admin).
Not exactly world-class software.