I incorrectly assumed there was a regression in the SDK when I couldn't do a multisig tx (cosmos/cosmos-sdk#4391). Turned out I was using the wrong key! Totally my fault for not actually believing the error, but might be nice if the error had more info.

The error is currently: provided key didn't exist in pubkeys, but would be nice if it said specifically which key didn't exist, and maybe even listed the set of keys.