Weird behavior OMEMO while using MAM Openfire

Question

I am experiencing a strange behavior while using the Monitoring plugin. Messages archived in the database sometimes cannot be decrypted.
Situation:
Chatroom with 3 members.
1 member uses gajim on Windows
2 members use Snikket on IOS

The gajim user is always able to decrypt messages no matter who of these 3 members sends a message and messages sent by this user can also always be decrypted through all members. I assume because the user is permanently online. (PC is always turned on and gajim is running)

Problem exits exclusively among iOS (Snikket) users. Sometimes they are able to decrypt their messages and sometimes they don't. I am struggling now since weeks with that and have no clue where it sticks. No matter if user 1 or 2 is offline, detached what ever I have been trying out every possible situation. It just happens that one message is readable the next message is not instead.

Taking a look into the table ofMessageArchive reveals for every message the correct information. Device, key, payload, all you need is in there, however the devices are not able to decrypt their related messages. Again, the weird thing is that it just happens sometimes after being offline.

I don't know if the issue is related to the monitoring plugin, actually I don't even think so. It seems that the keys the messages are have encrypted with are not correct.

Versions:

  RedHat 8
  MariaDB 8
  OF 4.7.1
  Newest Monitoring Plug-in
  Snikket 1.2 build 10
  2 iPhones xr iOS 15.4.1