Notification - received all but not the last one

Hello everyone,

Notifications are working and I receive all messages but not the last one.
It’s like the last message is buffered and when a new one is coming graylog sends last but one. For example: in alertlog I have ORA-1, ORA-2, ORA-3 and i receive notification for ORA1, ORA-2 but not for ORA-3. When ORA-4 is written in alertlog I receive notification for ORA-3 and so on.
I see them in stream and in /var/lib/graylog-server/journal/messagejournal-0/00000000000000000218.log but notification for last message is not triggered.

There are no errors in graylog server or any other component.
Any thoughts? Please help! Thank you!


Config:
Graylog 3.3.6
Sidecar Version 1.0.2
Elasticsearch version number: 6.8.11
mongod --version db version v4.4.0