When cache expires, theme breaks!

Hi there,

I’ve recently narrowed down the cause of my problem and was wondering if I could (again) ask for your help.

I recently backed up my entire site and was forced to restore from said backup. I’m running a lightly modified theme. Now I find that when I erase the ‘cache’ folder (or it erases itself), my theme “breaks” and I am forced to revert to the default theme. Does anyone know why this is happening? Thanks for your time- https://www.zhukovvideo.org/home