file upload failed. (API upload did not contain a file part)

Hello, I'm paul bae.

file upload frequently failed with java rest template.

not everytime. sometimes success with exactly same request(without filename).

every failed http code is "400" and message is "API upload did not contain a file part".

I don't know how to fix it. 

belows are test upload fail log.

Request body: --ZCmcwgj21ZGAdw-F5nPyOHYyjoSbz64IvypjSJMc
Content-Disposition: form-data; name="attributes"
Content-Type: application/json;charset=UTF-8

{"name":"upload-test-20220806145130","parent":{"id":"164677862892"}}
--ZCmcwgj21ZGAdw-F5nPyOHYyjoSbz64IvypjSJMc
Content-Disposition: form-data; name="file"; filename="upload-test-20220806145130"
Content-Type: application/octet-stream
Content-Length: 1000

abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl
--ZCmcwgj21ZGAdw-F5nPyOHYyjoSbz64IvypjSJMc--

Response body: {"code":"bad_request","help_url":"http://developers.box.com/docs/#errors","status":400,"message":"API upload did not contain a file part","type":"error"}