A bug causes Aloy to move far off to the left or right side of the screen annoyingly changing movement direction and occasionaly changeing sides. This isn't a fix, but it can help make it much more managable and the game playable.
How to Fix Camera Issues
In many 3rd person games it is a common practice to move the camera during certain activities to keep the character from obstructing the player's view. Horizon Zero Dawn does the samething but has a bit of an issue with this. If you have this issue you may notice that Aloy is WAY to the left of center and movement is off to the left, (most of the time) and may occasionaly move to the right with the opposite affect.
This is because during common actions like aiming and using Focus, Aloy is moved to the left, freeing the middle of the screen for you to see. But like I said this is common. The issue, is that for what ever reason the camera doesn't recenter on Aloy, leaveing her on the left side when coming out of those activities.
This also occurs when moving with the 'a' or 'd' keys. When going left with 'a' Aloy is moved slowly to the right of the screen, alowing you to see where you are going a little better. But, it doesn't recenter afterwards. The same can also be said about the other way. Going right with 'd' moves Aloy to the left side of the screen, again not recentering afterwards.
What to Do with This Information
Thankfully when moving with 'a' or 'd' the camera shift isn't immediate, but rather a gradual process that takes a couple of seconds. Meaning that with 'a' and 'd' and a bit of fiddling you can recenter Aloy yourself whenever you want.
Don't like Aloy so far left? Walk right by holding 'd' until she is centerd/just under the eyeball and let go. Bam, centered. Or atleast untill you need to aim again.
To far right? just do the same by walking left with 'a' until centered.
From what I understand the devs are now aware of this bug and are working on it so this is should only be a temperary problem and fix.