I see it on my XL STX but it looks intentional. If you look at the edges where it starts, you can see the plastic moving away. There also appear to be slats that look like they are holding it out there. Note that I have the all black mirrors, don't know if the different mirrors (the chrome ones like on your Lariat) are supposed to be different.Don't have that issue on my lariat. Curious if you pressed on it to see if there is movement? Might be loose nuts of the inside if they still attach like the older Rangers mirrors did.
The gaps are different on each side. More of a gap on the driver side than the passenger side.I see it on my XL STX but it looks intentional. If you look at the edges where it starts, you can see the plastic moving away. There also appear to be slats that look like they are holding it out there. Note that I have the all black mirrors, don't know if the different mirrors (the chrome ones like on your Lariat) are supposed to be different.