Channels with unread messages do not appear bold and bright

Summary
Channels with new messages do not appear bold/bright.

Steps to reproduce

  1. Somebody writes a new message in a channel.
  2. Another person opens Mattermost.

Expected behavior
The Channel where somebody different wrote a message should appear bold and brighter within Matttermost.

Observed behavior
All channels appear the same. Even those with unread messages.
If one is mentioned it shows under “Threads” but the Channel itself stays the same.
However it is possible to mark a channel as unread – then they appear bold and bright.

The problem appeared after migrating to a new server. This migration was done with mmctl export and mmctl import.