Have you noticed that sometimes your iMessages are not in the order you received them? It only happens when you're having a message conversation with someone that goes back and forth quickly; when the sequence is most important.
This “bug” was introduced with the iOS 11.2.1 update, and Apple included a fix in the iOS 11.2.5 update on January 23, 2018. However, for many people the fix didn’t work because there are a few extra steps you need to take on your iPhone.
Here are the steps to get messages back in order on your iPhone:
Step 1 - Make sure Your iOS Software is up to date
Go to Settings > General > Software update > and update your software if necessary.
Step 1 - Turn Messages on and off
Go to Settings > Messages > Turn off messages. Wait 10-15 seconds. Turn it back on.
Step 2 - Turn Time Settings on and off
Go to Settings > General > Date & Time > Turn off Set Automatically for about 10-15 seconds and turn it back on.
Step 3 - Restart your iPhone
Hold down the sleep/wake button on the upper right side > sliding to power off > hold down the sleep/wake button until the Apple logo appears.
Grab a friend and have a quick back and forth message conversation to make sure everything is back in order.