Hi Duncan,
I did not expect for you to still be having this problem as the original post was 10 months ago. I did this mostly for my records if I run into the problem in the future. However, I will expound upon how I diagnosed this in hopes it may provide you (or anyone else) with some help. First, locate installed packages which are related to "dansguardian" or "content filtering" with this command

Next, find files from these packages which are different from the original. Like this

Here is a good page to explain the nomenclature. https://www.novell.com/coolsolutions/feature/16238.html
Since the lists and conf files have been updated after being installed, they can be ignored. This leaves the fancydmtemplate.html and template.html, and deduced a missing resource (zeroed out file) could very likely cause a segfault. More than happy to help if this does not remedy your segfaults.
Actually, the first thing I did was to run mprime overnight to make certain it was not the RAM, as Tim had suggested. Tim Burgess is very knowledgeable with ClearOS -- may even be one of the developers -- usually Tim's advice is correct when I have an issue, it just happened to not be the case in my situation this time. If you have not run memtest86 or mprime against the hardware for 10+ hours without fault, then you may also want to check this. Hope this adds some clarity and help!
Sincerely,
John

Hello all,
For me, this issue was not related to RAM, but instead to having zeroed out template files. The exact errors looked like

The elements which remained the same were

router kernel: dansguardian-av

segfault at fffffffffffffff8 ip

sp

error 5 in libstdc++.so.6.0.19