How to get error code 400700

Hi sendbird,
on api documentation, I saw error code 400700

400700 (BlockedUser.SendNotAllowed)
The request cannot be completed because the blocked user is trying to send a message to the blocking user.

I did some experiments, for 1:1 group chat, if A blocking B, when B(the blocked) tries to send message to A (the blocking), I never saw any 400700 error returned. the message delivered to the channel, just A is not able to see it.

How could B get this 400700 error code? in my application, I want B knows he got blocked .

Any help would be greatly appreciated.

Does anybody knows anything about this error code? thanks a lot for your help!