DELETE event is not propagated to the client

[shirli_om2]

We have a command-based adapter set up with a client subscribing to specific item.
The sever send ADD and UPDATE commands which propagate successfully to the client with the specific key.

But when the server send a DELETE command with the same key the event is not propagated to the client.

What can be the reason the DELETE not passed on to the client side?

IMPORTANT NOTE : If the client side subscribed with subscription type MERGE (instead of COMMAND) then the event with DELETE command is sent successfully to the client.