Unconsistent history between browsers

What's happening?

On firefox, I cannot find some messages I posted a few minutes ago. Reload does not fix it. On chrome, logging-in with the same user and I can see them.

Steps to reproduce

Not sure about the reproduction steps though. Look inconsistent. It's sad :-(

Relevant logs and/or screenshots

Associated chrome and firefox screenshots:

As you can see there are additional messages on Chrome compared to Firefox. Seems that Matthieu received them actually so I guess they are actually present in the history.

Your Environment

I experienced that on https://community.startinblox.com, SIB-Core channel.

• Browser name and version: Firefox version 75.0
• Operating System and version (desktop or mobile):
  • Ubuntu Desktop 18.10