I noticed a bug in edge (v2.2.0) where asset_id timestamps were missing from my rails app, this only happened for me when using relative_url_root set to some value.
I've created a lighthouse ticket and patch attached to the ticket. It's a very simple fix so hopefully it can make it into the build for v2.2.1
Here's the ticket: http://tinyurl.com/558um7
-- Joe