iOS Post to Facebook shows m facebook com

Question

My iOS app is posting an in-app post of ours from our app to Facebook using the Social framework and the following code.

It successfully posts to Facebook and correctly deep-links back into our application. The issue is that when this post is viewed on the Facebook iOS mobile app, instead of displaying the post's caption or description, we are seeing "m.facebook.com" as shown in this screenshot. We'd like to remove or replace "m.facebook.com" with either caption, description, or our site's root URL.

I"m guessing this "m.facebook.com" URL root is coming from the deep link URL, which is "https://m.facebook.com/apps/(our-app)/?deeplink=postId:(post-id)". We want it to deep link, but don't want "m.facebook.com" to be displayed.

Any advice? Thanks.