Github bug: Task progress bar not showing after description updated through API?

repro.md

1. Created Pull Request #1

2. Called the API with curl -v -u Novex -X PATCH -d '{"body": "- [ ] An incomplete task"}' https://api.github.com/repos/Novex/TasklistTest/issues/1

* STATE: INIT => CONNECT handle 0x80047718; line 1028 (connection #-5000)
* Hostname was NOT found in DNS cache
*   Trying 192.30.252.127...
* STATE: CONNECT => WAITCONNECT handle 0x80047718; line 1076 (connection #0)
* Connected to api.github.com (192.30.252.127) port 443 (#0)
* successfully set certificate verify locations:
*   CAfile: /usr/ssl/certs/ca-bundle.crt
 CApath: none
* SSLv3, TLS handshake, Client hello (1):
* STATE: WAITCONNECT => PROTOCONNECT handle 0x80047718; line 1189 (connection #0)
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Server key exchange (12):
* SSLv3, TLS handshake, Server finished (14):
* SSLv3, TLS handshake, Client key exchange (16):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* Server certificate:
*        subject: C=US; ST=California; L=San Francisco; O=GitHub, Inc.; CN=*.github.com
*        start date: 2014-04-08 00:00:00 GMT
*        expire date: 2017-04-12 12:00:00 GMT
*        subjectAltName: api.github.com matched
*        issuer: C=US; O=DigiCert Inc; OU=www.digicert.com; CN=DigiCert SHA2 High Assurance Server CA
*        SSL certificate verify ok.
* STATE: PROTOCONNECT => DO handle 0x80047718; line 1208 (connection #0)
* Server auth using Basic with user 'Novex'
> PATCH /repos/Novex/TasklistTest/issues/1 HTTP/1.1
> Authorization: Basic AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
> User-Agent: curl/7.37.1
> Host: api.github.com
> Accept: */*
> Content-Length: 36
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 36 out of 36 bytes
* STATE: DO => DO_DONE handle 0x80047718; line 1281 (connection #0)
* STATE: DO_DONE => WAITPERFORM handle 0x80047718; line 1407 (connection #0)
* STATE: WAITPERFORM => PERFORM handle 0x80047718; line 1420 (connection #0)
* HTTP 1.1 or later with persistent connection, pipelining supported
< HTTP/1.1 200 OK
* Server GitHub.com is not blacklisted
< Server: GitHub.com
< Date: Tue, 17 May 2016 00:50:21 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 2055
< Status: 200 OK
< X-RateLimit-Limit: 5000
< X-RateLimit-Remaining: 4998
< X-RateLimit-Reset: 1463449623
< Cache-Control: private, max-age=60, s-maxage=60
< Vary: Accept, Authorization, Cookie, X-GitHub-OTP
< ETag: "36521787bddb4ea332b7853de43006bc"
< X-GitHub-Media-Type: github.v3
< Access-Control-Expose-Headers: ETag, Link, X-GitHub-OTP, X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset, X-OAuth-Scopes, X-Accepted-OAuth-Scopes, X-Poll-Interval
< Access-Control-Allow-Origin: *
< Content-Security-Policy: default-src 'none'
< Strict-Transport-Security: max-age=31536000; includeSubdomains; preload
< X-Content-Type-Options: nosniff
< X-Frame-Options: deny
< X-XSS-Protection: 1; mode=block
< Vary: Accept-Encoding
< X-Served-By: 3e3b9690823fb031da84658eb58aa83b
< X-GitHub-Request-Id: DCF5EC9A:7F8F:4511CA5:573A6ACD
<
{
 "url": "https://api.github.com/repos/Novex/TasklistTest/issues/1",
 "repository_url": "https://api.github.com/repos/Novex/TasklistTest",
 "labels_url": "https://api.github.com/repos/Novex/TasklistTest/issues/1/labels{/name}",
 "comments_url": "https://api.github.com/repos/Novex/TasklistTest/issues/1/comments",
 "events_url": "https://api.github.com/repos/Novex/TasklistTest/issues/1/events",
 "html_url": "https://github.com/Novex/TasklistTest/pull/1",
 "id": 155152867,
 "number": 1,
 "title": "Update README.md",
 "user": {
   "login": "Novex",
   "id": 564860,
   "avatar_url": "https://avatars.githubusercontent.com/u/564860?v=3",
   "gravatar_id": "",
   "url": "https://api.github.com/users/Novex",
   "html_url": "https://github.com/Novex",
   "followers_url": "https://api.github.com/users/Novex/followers",
   "following_url": "https://api.github.com/users/Novex/following{/other_user}",
   "gists_url": "https://api.github.com/users/Novex/gists{/gist_id}",
   "starred_url": "https://api.github.com/users/Novex/starred{/owner}{/repo}",
   "subscriptions_url": "https://api.github.com/users/Novex/subscriptions",
   "organizations_url": "https://api.github.com/users/Novex/orgs",
   "repos_url": "https://api.github.com/users/Novex/repos",
   "events_url": "https://api.github.com/users/Novex/events{/privacy}",
   "received_events_url": "https://api.github.com/users/Novex/received_events",
   "type": "User",
   "site_admin": false
 },
 "labels": [

 ],
 "state": "open",
 "locked": false,
 "assignee": null,
 "milestone": null,
 "comments": 0,
 "created_at": "2016-05-17T00:37:29Z",
 "updated_at": "2016-05-17T00:50:21Z",
 "closed_at": null,
 "pull_request": {
   "url": "https://api.github.com/repos/Novex/TasklistTest/pulls/1",
   "html_url": "https://github.com/Novex/TasklistTest/pull/1",
   "diff_url": "https://github.com/Novex/TasklistTest/pull/1.diff",
   "patch_url": "https://github.com/Novex/TasklistTest/pull/1.patch"
 },
 "body": "- [ ] An incomplete task",
 "closed_by": null
}
* STATE: PERFORM => DONE handle 0x80047718; line 1590 (connection #0)
* Connection #0 to host api.github.com left intact

3. Problem: Would expect to see in the PR List

4. Manually edit another task into the description through Github Web

5. Task list is correctly updated