I've the same problem. Any feedback from the support?
Didn't get called back. I still prefer my own file/handler though (someone else did this implementation initally) so I won't change it back even they get it working.
Would you like to share your fileinformation.aspx?
I upgraded SiteSeeker libraries from 22.214.171.124 to 126.96.36.199.
The site was using this type of solution to add a custom meta tag for UnifiedFile:
After upgrade I got this error on startup: "This operation is only valid on generic types"
I solved it by using my own "siteseeker/fileinformation.aspx"-ish file but a bit annoying that things break without notes in the release log.
Still waiting for a call back from support...