GMT cohorts and automation success ghosts
Day-one success can move when clocks and bot IDs move—not when the workflow does.
Teams serving UK operations often mix UTC warehouse timestamps with GMT or BST product calendars. A cohort day that spans the wrong midnight shifts every success cell without anyone shipping a feature.
Runner upgrades that change anonymous-to-known stitching create similar ghosts: returning cases appear as new cohorts, and week-four rates look healthier or worse depending on merge rules.
Before celebrating an automation success lift, list runner versions, identity rules, and timezone settings beside the chart. If those moved, treat the chart as suspect until you rebuild the cohort from raw events.