Activity tab on pull request error on load

The tab says

Error
We were unable to load this page.

Inspecting the network requests shows that there's some HTML that comes back. It includes this:

<p>This might be useful in debugging the problem:</p>
<p><code>f4934185f9e0499ba2eebaa6c9a7db59</code></p>I don't get this on all PRs, just on some (may be related to BCLOUD-8611 - both issues happen on the same PR).