Customer sees ServerErrorResponseException error after successful payment

After successfully completing payment with credit card, the customer sees an error message

The top message in blue says: “Successfully applied payment.”

But the bottom says Guzzle\Http\Exception\ServerErrorResponseException

Screenshot:
https://s3.amazonaws.com/4rk/screen-shot-2019-02-06-09.49.49-wy8849m9.png

This was the URL where that screen / error showed:
https://fin.invoice.services/view/

Additional Context:
The payment did go through, the customer got a confirmation email, and I see the payment in my Stripe dashboard.

I am accepting payments through Stripe gateway.

Do I have something mis-configured or is this an application bug?

I am hesitant to start billing all of my customers and have them see this.

This is the first report I’ve heard of this issue.

I suggest using the test Stripe keys to see if you can reproduce the problem.