It appears the UI.X sidebar is stuck in "landscape mode" for mobile users.
I believe it has something to do with the "New Posts" sidebar component (the one built into XF), the page gets stretched when a thread title is really long, but on the XF default theme, that thread title gets shortened and the page looks fine.
For example, on the Xenforo default theme, a thread title about "Legos" is shortened whilst the full title shows up on the UI.X theme.
On the Xenforo default theme it shows the title like this:
"Can you find the Le..."
And on UI.X it shows up like this:
"Can you find the Lego dog in the Lego pandas?"
(It'll have the entire title showing and won't shorten it like the other themes do)
Again this only happens from mobile view and when the user is not in landscape mode. I am using UI.X version 1.5.4.0
Any ideas on how to fix this?