I am having a little problem with iMessage notifications between my iPhone 6 and my Apple Watch.
In the case my iPhone 6 stay in locked screen while I am still wearing the Watch, iMessage notifications should appear on the Watch only. I mean I having notifications on both devices. This happens on just iMessage notification only.
I do need some helps.
This was my problem. I just disable and then reactivate message on lockscreen from my iPhone.
Go to Settings ----> tab on Notifications ----> Select Messages ----> at Show on Lock Screen, toggle this off, wait a few seconds, then toggle back on. This work on me somehow and I have never faced the same situation again since that day.