Subrequest to /redis-store failing - rc=403

[JeffCleverley]

Started seeing more of these cropping up, have a specific url, and the cache always returs a MISS and STORE, but it never stores due to this.

It only happens on one URL with this site.

srcache_store subrequest failed: rc=403 status=0, client: [IP], server: [post url], request: “GET /[post url]/ HTTP/1.1”, subrequest: “/redis-store”, host: “[site]”