Error code with no message

I tried submitting a post here and an error message comes up, or at least a placeholder for one. There is no actual message, just a red bar where you’d expect a message to go.

I thought maybe the captcha was the issue (as has been in the past on this site) but I removed it and it still happens. Also, I still get spam submissions from bots, not sure how it’s possible?

The page I need help with: [log in to see the link]