Post archive rendered blank

Quack,

We got a message with a blank content here: https://lists.ovirt.org/archives/list/users@ovirt.org/message/YLPWQQ5FU2P3NEHDFL54P6M2WQVAXOOS/

It should have rendered like this: https://www.mail-archive.com/users@ovirt.org/msg52306.html

In the logs I got no error:

INFO 2018-11-26 06:38:59,593 16214 hyperkitty.views.mailman Archived message <1543235855.11158.2.camel@prismatelecomtesting.com> to https://lists.ovirt.org/archives/list/users@ovirt.org/message/YLPWQQ5FU2P3NEHDFL54P6M2WQVAXOOS/

In the Firefox webconsole there are no errors either.

Without an error message and as everything is automagically loaded via JS, not being a webdev I'm a bit at a loss to know how to debug this. Could you give a hand please?

\_o<