ODK Central server no longer allowing form preview or form submission

Hi ODK Forum, I'm experiencing some issues with an ODK Central server that was previously working just fine. In essence I'm no longer able to preview or submit forms that up until last night were working fine. Please see the details below. Thanks in advance for any help, pointers or suggestions.

1. What is the problem? Be very detailed.
I have an ODK Central server that was working fine last night. This morning it appears that we can no longer preview forms that were previously previewable and when clicking "Preview" in ODK Central we now get the error:

"Loading Error. Error Occurred during the loading of this form. It is recommended not to use this form for data entry until this is resolved. Please contact errors@getodk.org with the link to this page and the error message below: Bad Gateway".

In addition, forms that I was able to submit last night using ODK Collect are now throwing the error: "Error: Generic Exception: Error: Internal Server Error (500) at https:// ..."

When I upload new forms into the ODK Central server, the "Preview" button for those forms is greyed out in perpetuity and if I hover over this it says "Preview has not finished processing this form."

2. What app or server are you using and on what device and operating system? Include version numbers.
I am Using ODK Central v1.0 deployed on an Amazon server.

3. What you have you tried to fix the problem?
I've tried reloading the forms, but as described above, they are not previewable either.

4. What steps can we take to reproduce the problem?
I'm not really sure about this question. I suspect that something is wrong with Enketo (probably my particular setup) - I'm not sure if I need to set up an account with Enketo and perhaps I have run out of Quota? If so, can someone point me to instructions on how to resolve this?

5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.

What size machine (CPU, RAM) do you have? Have you tried a reboot?

Thanks for the input @yanokwa - I think you've led me to find the issue... the ODK Central server is completely out of disk space (it was a small test server on AWS). I'm trying to increase the disk space available on the root partition, but unfortunately, I can't do that until I free some disk space up (a catch 22). Is it possible for me to delete the contents of my existing projects in the ODK Central server? These currently contain dummy data, so I don't mind losing all of that for now. Once I've done that I can increase the size of my root partition. Any advice greatly appreciated.

Since you don't care about the data, I'd probably throw away the central folder and start over. Or throw away the machine and get a more appropriately sized one.