I was transferring zip files to an external hd a few days ago and Endless suddenly went into emergency mode.
I’ve attached three photos of what I’m seeing. Apologies, they are not of very good quality. On phot. 3, I can see: Failed - Failed to start EOS Prepare OS/. and a number of failed dependencies, including: /sysroot.
Unfortunately, this looks like a hardware fault to me, too. If possible, I suggest you create a bootable USB stick on a different computer – here are instructions to make an Endless OS USB stick on any Linux distribution, and there are similar FAQs for Windows and macOS – and use this to back up data from your Endless OS computer, then contact the hardware vendor.