Error when trying to upvote posts/comments?

Howdy,

For awhile now (possibly even since I started using kbin in June) I've run into an issue where if I stay on a page for too long and then try and upvote something,I instead get taken to an error page. If I then go back to the page I was just on, refresh the page, and then upvote the comment/post it'll usually work. Sometimes the error shows up after staying on the page for 10+ minutes, sometimes it can happen after being there for just a minute.

Is this a known bug? It happens to me on both mobile and PC (both using Firefox).