Over the Christmas break Our IT people applied upgrade to ubuntu 16.04 and setup webwork (2.12) so we can use CAS. This semester, any problem with a static image is very slow to render, up to 45 seconds. All problems with Dynamic images are just fine.
For static images the hang up seems to be the time to generate the alias/link
in wwtmp/COURSE/images to the static image. Once that is generated there is no problem loading the image as you can paste that link into a browser and the image displays just fine so the link to the static image is being created, just seems to take a long time.
We have CAS turned on in some courses and not in others, this doesn't seem to make any difference.
Any help would be great as we are in the middle of the semester and have lots of frustrated students this weekend.