Unable to use the UI on a WD MyCloud

When I try to access the admin interface for my Weste Digital "My Cloud" NAS, the page is stuck on

"Reading configuration information..."

Looking a the console, I can see two 500 errors:

I'm unsure as to when the issue first appeared, I found out when trying to access it to reactivate SSH access.

It used to work fine, I may have broken something via SSH (I did an apt-get update and install).