Most likely Displayed chat markers issue is caused by notifications being shown and dismissed or not shown but dismissed while posting it. That was triggering marking messages as "read" which could result in the Displayed chat marker being sent.

As a solution, we will change how notifications work:

1. Notification dismissal will not mark messages as read - it will just dismiss notification, as in Messages app.
2. Opening conversation will dismiss all notifications related to this conversation, but it will not mark messages as read. Only those which were actually displayed will be marked as read.
3. Incoming chat markers with displayed will dismiss only notifications that were received before this message.

Seems to be fixed