Windows Autopilot: notes from the field

We have machines being sent from a reseller, and the first time we Autopilot them, they go through the standard OOBE - asked about location services, telemetry, and so on. The sign on screen is generic, not specific to our Tenant. Only after they are well into the process do they get the ESP. If you don't sign in to the generic login screen and reboot them, sooner or later they suddenly realise they are Autopilot and offer the correct sign on screen. After that, even after a device reset, they always do the right thing. What can we do to fix this and deliver a consistent end user experience?