Broken themes in 2.1.10
I'm working on an older forum, v2.1.10 (I'm working a plan to upgrade to 3.x) but recently an incident occurred that seems to have broken most themes. The default theme works but none of the others do, as well as none of the mobile themes, it just produces a blank screen. I suspect something is wrong with Smarty but need some help diagnosing the issue.
The cause of the problem was a security incident on the server which required me to restore a backup of the vanilla files. I simply overwrote what was there with a backup from a few days earlier. Everything else works except for some themes.
I've verified there's a /cache/Smarty/cache folder and a /cache/Smarty/compile folder, both have the correct permissions. I'm at a loss, does anyone have some ideas for me?