Thank you jharrington7897​!I can confirm that the Appmeasurement.js is loading before s.Visitor.js when fid is fired and is not when mid is fired. This appears to be our issue.Great lead.

To follow up here, if I have cookies set on a first-party domain for s_vi, s_fid, AMCV and AMCVS but my site is firing the Fallback ID from s_fid in the network call, what might be happening?Assuming all of these primary Visitor IDs are present, but the call to metrics.domain.com uses the fid, will my unique visitors be inflated?