I've provided some detailed information to Rackspace about instance UUIDs which hit this and the various other failures marked as duplicates, and they're hunting for an underlying cause. According to their logs we're booting these instances from the snapshots we request, but we're seeing strong evidence to suggest that they're actually booting from older snapshots we've deleted entirely. Also we're only witnessing this behavior in their DFW region, but not the other regions where we have identical setups.
I've provided some detailed information to Rackspace about instance UUIDs which hit this and the various other failures marked as duplicates, and they're hunting for an underlying cause. According to their logs we're booting these instances from the snapshots we request, but we're seeing strong evidence to suggest that they're actually booting from older snapshots we've deleted entirely. Also we're only witnessing this behavior in their DFW region, but not the other regions where we have identical setups.