For anyone this might be helpful for, it turned out this was a caching issue. To resolve it this was taken out of the apache config file on our server:
LoadModule disk_cache_module modules/mod_disk_cache.so
# To enable a cache of proxied content, uncomment the following lines.
# See http://httpd.apache.org/docs/2.2/mod/mod_cache.html for more details.
#
#<IfModule mod_disk_cache.c>
# CacheEnable disk /
# CacheRoot "/var/cache/mod_proxy"
#</IfModule>
#
#<IfModule mod_disk_cache.c>
# CacheRoot "/data/sitename/cache"
# CacheEnable disk /
# CacheDirLevels 2
# CacheDirLength 1
#</IfModule>
Thanks–I’ll give that a try.
Thanks, Liam. I’ve already tried disabling all plugins and that didn’t resolve the issue.