Why isn't messages showing all incoming messages?

Frequently, when using Messages I am not getting all of the incoming messages that sent via iMessage.

For example, texting with a friend, I sent her a message, she responded. And, I saw the ... bubble, but didn't get a message. My phone, however, buzzed, and I was able to see a response.

Then, I got another message from her, but not the first response. It seems that Messages is intermittently dropping iMessage texts.

Is this a known issue?