Why is Auth0.js giving me payload validation errors "None of the valid schemas were met" and "Missing required property" on Passwordless/Verify?

My SPA Client is using the Auth0.js Passwordless Start/Verify flow to authenticate users. My auth callback page is receiving the below Payload Validation Error. I have verified the user exists for the SMS connection in the Auth0 Dashboard and that the SPA Client has the SMS connection enabled.

Error:

https://localhost:9001/auth/callback#error=access_denied&error_description=
Payload%20validation%20error%253A%20'None%20of%20the%20valid%20schemas%20were%20met'
.%20Inner%20errors%253A%20%5B%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20blocked'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20email_verified'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20email'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20verify_email'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20phone_number'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20phone_verified'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20verify_phone_number'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20password'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20verify_password'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20user_metadata'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20app_metadata'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20username'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20client_id'
.%20(also)%20Payload%20validation%20error%253A%20'Missing%20required%20property%253A%20groups'
.%20%5D.&state=statehash

Auth0 Initialization:

this.auth0 = new auth0.WebAuth({
                audience: `https://${authSettings.domain}/userinfo`,
                clientID: authSettings.checkoutClientId,
                domain: authSettings.domain,
                redirectUri: authSettings.checkoutCallbackUrl,
                responseType: 'token id_token',
                scope: 'openid email profile'
            });

Passwordless Start:

this.auth0.passwordlessStart({
        connection: 'sms',
        send: 'code',
        phoneNumber: phoneNumber,
        authParams: {
          responseType: 'token id_token',
          scope: 'openid email profile'
        }
      }

Passwordless Verify:

this.auth0.passwordlessVerify({
          connection: 'sms',
          phoneNumber: phoneNumber,
          verificationCode: confirmationCode,
          type: 'sms',
          authParams: {
            responseType: 'token id_token',
            scope: 'openid email profile'
          }
        }

The "missing required parameters" don't even make sense for a call to passwordless/verify.

Turns out the error was actually being thrown inside a custom Auth0 Rule but was only surfacing via the auth callback.

Specifically, we had a rule that called auth0.users.updateAppMetadata and auth0.users.updateUserMetadata which apparently do not work with Passwordless SMS connections.