Unable to merge accounts

[jiannynan96]

{
"type": "https://stellar.org/horizon-errors/server_error",
"title": "Internal Server Error",
"status": 500,
"detail": "An error occurred while processing this request. This is usually due to a bug within the server software. Trying this request again may succeed if the bug is transient, otherwise please report this issue to the issue tracker at: https://github.com/stellar/go/services/horizon/internal/issues. Please include this response in your issue.",
"instance": "horizon-002c/BFEiaaFONB-48132104"
}