ValidationErrorsCollection: Braintree I don't know why I'm getting this error

I'm using braintree in application. some time ago it worked without any problem. now it doesn't always work and when it doesn't. I get this error on console: ValidationErrorsCollection.
Node.js code

    const gateway = new braintree.BraintreeGateway({
        environment:  braintree.Environment.Sandbox,
        merchantId:   process.env.BRAINTREE_MERCHANT_ID,
        publicKey:    process.env.BRAINTREE_PUBLIC_KEY,
        privateKey:   process.env.BRAINTREE_PRIVATE_KEY
    });


    exports.generateToken = (req, res) => {
        gateway.clientToken.generate({}, function(err, response) {
             //Se verdade vamos trazer o token
                if(err){
                    res.status(500).send(err)
                }else{
                    res.send(response)
                }
        });
    };

    exports.processPayment = (req, res) => {
        let nonceFromTheClient = req.body.paymentMethodNonce
        let amountFromTheClient = req.body.amount

        //charge


        let newTransaction = gateway.transaction.sale({
            amount: amountFromTheClient,
            paymentMethodNonce: nonceFromTheClient, 
            options: {
                submitForSettlement: true
            }
        }).then(function (result) {
              if (result.success) {
                res.json(result);
              } else {
                  console.log(result.errors)
                //res.status(500).json(error); 
              }
              }).catch(function (err) {
                console.error(err);
              });

    }