I think I may have found another problem with the caching of vmlinux files. I am doing some testing but I think it may need a bit more work to ensure all modules are extracted and handle 32-bit on 64-bit machine properly. Right now I'm not sure how critical it is but it may result in modules not being extracted properly so it needs fixed.
I have tested both bugs 1314973 and 1313011 and they are fixed in retrace-server-1.15-1.el6
The issue I found is more extensive than just 32-bit vmcore kernel modules and should be fixed. I posted a patch that fixes the problem as described in https://bugzilla.redhat.com/show_bug.cgi?id=1368807#c14 and https://github.com/abrt/retrace-server/pull/149