Find that it fails to unfollow a question sometimes recently

Question

I am originally following a question (Spring JPA Auto Flush) . Then I click the Following status link in the question to unfollow it. A popup then display saying that You’re no longer following this question. But after I refresh the page , I am still following this question.

HTTP request that sent out after I click the Following status link to unfollow :

POST https://stackoverflow.com/posts/77168898/vote/21
content-type: application/x-www-form-urlencoded; charset=UTF-8

With the following form data:

fkey=48eb00f4fe7b0afb3608840be5f59e909500fe5bfa6c5e9a9def0b5a6254cb9b

And the received HTTP response is 200 with the following content :

{
  "Success": true,
  "Reason": 0,
  "Warning": false,
  "NewScore": 0,
  "Message": "\r\n<div class=\"s-popover p0 py12 js-following-confirm s-anchors s-anchors__default\" id=\"divFollowingConfirm-77168898\" role=\"menu\">\r\n    <div class=\"s-popover--arrow\"></div>\r\n        <h5 class=\"bold mb4 px12\">You&#x2019;re following this question</h5>\r\n    <p class=\"mb12 px12\">You&#x2019;ll receive notifications when there&#x2019;s activity on this post.</p>\r\n    <p class=\"mb12 px12\">Manage followed posts in your <a href=\"/users/current?tab=following\" class=\"px0 fc-blue-600\">profile</a>.\r\n    </p>\r\n    <p class=\"mb0 pt12 px12 bt bc-black-100\">\r\n        <button id=\"btnUnfollowPostConfirm-77168898\" type=\"button\"\r\n                class=\"s-btn s-btn__link js-unfollow-post-confirm js-gps-track\"\r\n                data-gps-track=\"post.click({ item: 16, priv: 17, post_type: 1 })\">\r\n            Unfollow\r\n        </button>\r\n    </p>\r\n</div>\r\n",
  "CanOverrideMessageWithResearchPrompt": false,
  "Refresh": false,
  "Transient": false,
  "Info": false,
  "HasAcceptedByModRights": false
}

It only happens sometimes but not always.