@DerCommander and @aman18narang, that's definitely you or somebody else with your number is running Whatsapp somewhere else.

The fact that DerCommander doesn't receive messages when he's offline is because he's online somewhere else and those messages were received somewhere else.

The first thing I should try is close Yappari and tell somebody that's with you to send you a message. If that person shows a double checkmark then definitely you're running Whatsapp somewhere else (even if you don't know).

Another thing you should do, type: ps aux | grep Yappari

Yappari should appear just one time, are you running Yappari several times without knowing it?

The log from aman18narang clearly says that his connection was replaced for a new one. Other device definitely did it. There's no other way to get that error.