When an EDU comes in with updated cross-signing keys for a user, it's handled by the federation_inbound worker which lacks the ability to write the keys to the db. Stack trace: https://gist.github.com/dbkr/d93c32abab600ff3c7a240c0de0f1d61

@erikjohnston sez:

ah, looks like we're incorrectly registering an edu handler on workers when it should only happen on master

This affects ability to cross-sign to/from matrix.org so is time-sensitive.