There are only a couple of my animations that have root motion built in - two examples are the aiming animations from high cover. The character pops out and it’s useful to have root motion so the character actually moves out of cover.
This works correctly, however just afterwards something odd happens - the character, while holding the pose, slides backwards towards the old position. Why is this happening and how can I stop it?
You can see what’s happening in this picture. the root as moved, but the orange line represents some sort of tether to the old position which pulls the character in.
because your not using root motion, Your character is sliding back to where, your capsule is, that still didn’t move. You have to enable root motion on the montage, and depending what version you are using, the animation BLueprint must also have it enabled.
-Also when you do get it to play, sometimes it doesn’t want to work properly. I found a technique to get the root motion to fully work, is to set the movement to Flying. This makes sure all the animation will play without gravity affecting it.
Hope this helps! Cheers 
This has helped to some degree, I no longer have the problem shown in the picture, the root successfully updates with the character. however the sliding still happens! I have no idea why!
it seems the root is moving away from the capsule, but I have enabled root motion!
Make sure you’ve set Root Motion Mode to Root Motion from Everything in the anim blueprint editor window in the graph tab of the animation blueprint. and make sure you select edit defaults and not edit preview at the top for this - easy to miss.