From checking server logs i saw:
2018-06-01 09:17:26.909 /cos/v1/pay request to create the payment got a 503 status code
2018-06-01 09:18:43.046 /v2/refund request to refund payment got 499 status code
2018-06-01 09:20:03.250 /v2/refund request attempted again, got 499 status code
2018-06-01 09:23:00.731 /cos/v1/pay request is attempted again by the device and succeeds
After 2018-06-01 09:23:00.731 I would expect the refund request to succeed.
I'm not familiar with remote pay java, not sure what you can do to mitigate this.
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