FirebaseRemoteConfig Error "No value of type 'String' exists for parameter key"

Firebase answer to my bug report:

It seems that you're getting some warning about Remote Config. We managed to reproduce on our end, and our engineers have confirmed that this is working as intended. This happens because the Performance Monitoring SDK was added on your app. This is because Performance Monitoring uses Firebase Remote Config internally. However, our engineers have confirmed that they will try to reduce these warnings in the future. For now, you can ignore these as it's only a warning, and should not affect the app's performance.

It comes from last versions of firebase-perf (for example, 16.2.5), because it has internal firebase-remote-config dependency. I have the same issue, but I don't know how to properly fix this log spam (except "Fold lines like this" option in logcat). I hope Firebase team will fix it soon.