Intermittently get "no valid crumb was included in the request" when using Jenkins through the web browser

[Jordan Soet]

I regularly get the error "no valid crumb was included in the request" when
I'm using Jenkins through the web browser. This can usually be worked
around by going back, making the same changes again, then hitting save
again, but this is obviously annoying if I'm making any larger changes to a
job and then I happen to hit this error, as sometimes I'll forget exactly
what I just changed. Also, sometimes the second time (or 3rd time) it also
fails, but eventually it will always work. This happens when I'm regularly
using Jenkins, it's not a case that I leave the window open for a while and
then try and use the same session.

Anyway, when I google for this error I just get lots of results about
people who are trying to use Jenkins API, and such, but I'm just trying to
use Jenkins through the web interface, so I don't think I should get this
error. Is there something that I maybe have misconfigured on my jenkins
instance? Is there anything I can look into to see why I'm getting this
error?