javascript - 分块上传时直接500了

我用了js-multipart的DEMO是可以完成上传的， 但是我在用第三方组件上传的时候前面几个阶段都调试通了，就在最后一个请求 合并分块文件时， 这个请求直接返回500 我把参数都对了一次了都是对的，也没有错误码。

HTTP

Remote Address:183.2.206.56:80
Request URL:http://m0.api.upyun.com/chuhaiwang/
Request Method:POST
Status Code:500 Internal Server Error
Response Headers
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Connection:keep-alive
Content-Length:591
Content-Type:text/html
Date:Sat, 20 Feb 2016 01:50:45 GMT
Server:vivi/0.6
X-Request-Id:700b8e22a9047902930497770d124255
X-Request-Path:api-php-222, ctn-gd-dgg-025
X-Vivi-Streaming:on
Request Headers
view source
Accept:*/*
Accept-Encoding:gzip, deflate
Accept-Language:zh-CN,zh;q=0.8,en;q=0.6,zh-TW;q=0.4
Connection:keep-alive
Content-Length:154
Content-type:application/x-www-form-urlencoded
Host:m0.api.upyun.com
Origin:http://localhost:81
Referer:http://localhost:81/upyunchunk/test.html
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.85 Safari/537.36
Form Data
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view URL encoded
policy:eyJzYXZlX3Rva2VuIjoiYmY2ZWIzZTU4ZmNkMTExZWVhOTcwZThhOWFmNzVkN2YiLCJleHBpcmF0aW9uIjoxNDU1OTM2NTY5fQ==
signature:11a6e74f8b1c3ab2a792f967891e9437