I know bent chain hangers are a particular favourite of yours, but surely that'll only cause issues with indexing at the rear, which the OP says he doesn't have.Could you answer my question.
@nulleth , I see the video is with the bike upside down. (Either that or my monitor is broken). Does it make as much noise when it's he right way up? Is the chain, which is a 9 speed HG93, compatible with the chainset? (there are several Synapse models out there, so I can't see what transmission you've got).