Bot loss message

[1998-BossLee]

I submit a midjourney task in web, I want to get the message by jda.
If the prompt just text, such as 【cute dog】, I will get first message A by method【public void onMessageReceived(MessageReceivedEvent event)】, then the message A will update, I can get the update message by method【public void onMessageUpdate(MessageUpdateEvent event)】。Final, I will get the second message B.
However, when the prompt is 【imageUrl + text】，I cant get the first message A, just can get the second message B.
So I test differenct imageUrl, even more amazing, sometime I can get message A and message B, sometime I just get the second message B.
For example, this prompt can get 2 message【A and B】.【https://img1.baidu.com/it/u=427703835,1167333278&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=500 cute dog】.
Another prompt just get 1 message B.【https://img0.baidu.com/it/u=2704251234,795802980&fm=253&fmt=auto&app=120&f=JPEG?w=1200&h=800 cute dog】.
Does anyone know why this is happening?